Publications
| Title | Abstract | Year Filter | PMID(sorted ascending) Filter |
|---|
| measurement of the substrate dissociation constant of a solubilized membrane carrier. substrate stabilization of oxlt, the anion exchange protein of oxalobacter formigenes. | oxlt, a secondary carrier found in oxalobacter formigenes, mediates the exchange of divalent oxalate and monovalent formate. because oxlt has an unusually high turnover number (greater than or equal to 1000/s), and because formate, one its substrates, shows high passive membrane permeability as formic acid, it has been difficult to obtain information on protein-substrate interactions using traditional methods in membrane biology. for this reason, we devised a new way to measure substrate dissoci ... | 1992 | 1587833 |
| identification, purification, and reconstitution of oxlt, the oxalate: formate antiport protein of oxalobacter formigenes. | we had proposed earlier that the anaerobe oxalobacter formigenes sustains a proton-motive force by exploiting a secondary carrier rather than a primary proton pump. in this view, a carrier protein would catalyze the exchange of extracellular oxalate, a divalent anion, and intracellular formate, the monovalent product of oxalate decarboxylation. such an electrogenic exchange develops an internally negative membrane potential, and since the decarboxylation reaction consumes an internal proton, the ... | 1992 | 1587834 |
| cloning and expression of the oxalyl-coa decarboxylase gene from the bacterium, oxalobacter formigenes: prospects for gene therapy to control ca-oxalate kidney stone formation. | evidence suggests that the formation of calcium-oxalate stones in the urine is dependent on the saturation levels of both calcium and oxalate; thus, management of one or both of these ions in individuals susceptible to urolithiasis appears important. since there are no known naturally occurring enzymes in vertebrates capable of degrading oxalate, we have initiated a study to insert a plant-derived oxalate degrading enzyme gene into human cells as a means of lowering plasma and urinary oxalate co ... | 1991 | 2008903 |
| purification and characterization of formyl-coenzyme a transferase from oxalobacter formigenes. | formyl-coenzyme a (formyl-coa) transferase was purified from oxalobacter formigenes by high-pressure liquid chromatography with hydrophobic interaction chromatography and by deae anion-exchange chromatography. the enzyme was a single entity on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel permeation chromatography (mr, 44,000). it had an isoelectric point of 4.7. the enzyme catalyzed the transfer of coa from formyl-coa to either oxalate or succinate. apparent km and vmax valu ... | 1990 | 2361939 |
| purification and characterization of oxalyl-coenzyme a decarboxylase from oxalobacter formigenes. | oxalyl-coenzyme a (oxalyl-coa) decarboxylase was purified from oxalobacter formigenes by high-pressure liquid chromatography with hydrophobic interaction chromatography, deae anion-exchange chromatography, and gel permeation chromatography. the enzyme is made up of four identical subunits (mr, 65,000) to give the active enzyme (mr, 260,000). the enzyme catalyzed the thiamine ppi-dependent decarboxylation of oxalyl-coa to formate and carbon dioxide. apparent km and vmax values, respectively, were ... | 1989 | 2708315 |
| oxalate:formate exchange. the basis for energy coupling in oxalobacter. | in the gram-negative anaerobe, oxalobacter formigenes, the generation of metabolic energy depends on the transport and decarboxylation of oxalate. we have now used assays of reconstitution to study the movements of oxalate and to characterize the exchange of oxalate with formate, its immediate metabolic derivative. membranes of o. formigenes were solubilized with octyl-beta-d-glucopyranoside in the presence of 20% glycerol and escherichia coli phospholipid, and detergent extracts were reconstitu ... | 1989 | 2708365 |
| intestinal colonization of laboratory rats with oxalobacter formigenes. | six strains of oxalobacter formigenes (anaerobic oxalate-degrading bacteria) were examined for their ability to colonize the gastrointestinal tracts of adult laboratory rats. these rats did not harbor o. formigenes. strain oxcr6, isolated from the cecal contents of a laboratory rat that was naturally colonized by oxalate-degrading bacteria, colonized the ceca and colons of adult rats fed a diet that contained 4.5% sodium oxalate. five days after rats were inoculated intragastrically with 10(9) v ... | 1987 | 3435141 |
| microbial degradation of oxalate in the gastrointestinal tracts of rats. | rates of oxalate degradation by mixed bacterial populations in cecal contents from wild rats ranged from 2.5 to 20.6 mumol/g (dry weight) per h. the oxalate-degrading activity in cecal contents from three strains of laboratory rats (long-evans, wistar, and sprague-dawley) from four commercial breeders was generally lower, ranging from 1.8 to 3.5 mumol/g (dry weight) of cecal contents per h. this activity did not increase when diets were supplemented with oxalate. when sprague-dawley rats from a ... | 1987 | 3662516 |
| oxalate degradation by gastrointestinal bacteria from humans. | anaerobic bacteria that metabolize oxalic acid have only recently been isolated from the rumen and from other gastrointestinal habitats. they constitute a new genus and species, oxalobacter formigenes. this report presents the first comparison of cultural counts of these organisms from human feces and indicates that numbers as high as 10(7)/g may be present in feces from normal humans. rates of oxalate degradation by mixed bacterial populations in feces from seven normal humans ranged from 0.1 t ... | 1986 | 3950772 |
| oxalobacter formigenes gen. nov., sp. nov.: oxalate-degrading anaerobes that inhabit the gastrointestinal tract. | this report describes a new group of anaerobic bacteria that degrade oxalic acid. the new genus and species, oxalobacter formigenes, are inhabitants of the rumen and also of the large bowel of man and other animals where their actions in destruction of oxalic acid may be of considerable importance to the host. isolates from the rumen of a sheep, the cecum of a pig, and from human feces were all similar gram-negative, obligately anaerobic rods, but differences between isolates in cellular fatty a ... | 1985 | 3994481 |
| bacterial anion exchange: reductionist and integrative approaches to membrane biology. | studies of two different bacterial anion exchange proteins (antiporters) led us to conclude that both reductionist and integrative approaches contribute to progress in understanding membrane biology. we have used a reductionist perspective in applying cysteine scanning mutagenesis to probe individual amino acid positions of uhpt (uptake of hexose phosphate transporter), the carrier responsible for transport of glucose 6-phosphate by escherichia coli. this work has established experimental criter ... | 1994 | 7823041 |
| molecular cloning, dna sequence, and gene expression of the oxalyl-coenzyme a decarboxylase gene, oxc, from the bacterium oxalobacter formigenes. | oxalic acid, a highly toxic by-product of metabolism, is catabolized by a limited number of bacterial species by an activation-decarboxylation reaction which yields formate and co2. oxc, the gene encoding the oxalic acid-degrading enzyme oxalyl-coenzyme a decarboxylase, was cloned from the bacterium oxalobacter formigenes. the dna sequence revealed a single open reading frame of 1,704 bp capable of encoding a 568-amino-acid protein with a molecular weight of 60,691. the identification of a presu ... | 1994 | 8157618 |
| cloning, sequencing, and expression in escherichia coli of oxlt, the oxalate:formate exchange protein of oxalobacter formigenes. | oxlt is the oxalate/formate exchange protein that represents the vectorial component of a proton-motive metabolic cycle in oxalobacter formigenes. here we report the cloning and sequencing of oxlt and describe its expression in escherichia coli. the oxlt amino acid sequence specifies a polytopic hydrophobic protein of 418 residues with a mass of 44,128 daltons. analysis of hydropathy and consideration of the distribution of charged residues suggests an oxlt secondary structure having 12 transmem ... | 1996 | 8636101 |
| the relationship of oxalobacter formigenes and calcium oxalate calculi. | the intestinal oxalobacter formigenes were isolated in 30 cases of urolithaiasis and in 45 controls. the biologic characters and morphology of the bacteria were also observed. the results showed that the colony counts in urolith group 9 (mean 10(3)/g. faeces) were significantly less than that of controls (mean 10(8)/g. faeces) (p < 0.001). it is believed that the lesser amount of oxalobacter formigenes in urolith was the important factor of the calcium oxalate calculi formation. | 1995 | 8731936 |
| generation of a proton motive force by the anaerobic oxalate-degrading bacterium oxalobacter formigenes. | the generation of transmembrane ion gradients by oxalobacter formigenes cells metabolizing oxalate was studied. the magnitudes of both the transmembrane electrical potential (delta psi) and the ph gradient (internal alkaline) decreased with increasing external ph; quantitatively, the delta psi was the most important component of the proton motive force. as the extracellular ph of metabolizing cells was increased, intracellular ph increased and remained alkaline relative to the external ph, indic ... | 1996 | 8779588 |
| assimilation of oxalate, acetate, and co2 by oxalobacter formigenes. | oxalobacter formigenes is the only well-documented oxalate-degrading bacterium isolated from the gastrointestinal tract of animals. the production of atp by oxalobacter formigenes is centered around oxalate metabolism and oxalate is required for growth. a small amount of acetate (0.5 mm) is also required. oxalate is decarboxylated to formate plus co2 in nearly equimolar amounts. experiments were conducted to determine which potential carbon sources (oxalate, acetate, formate, co2) were assimilat ... | 1996 | 8941983 |
| evaluation of secondary structure of oxlt, the oxalate transporter of oxalobacter formigenes, by circular dichroism spectroscopy. | oxlt, the oxalate/formate exchange transporter of oxalobacter formigenes, was purified as a histidine-tagged variant, oxlthis, using ni2+-linked affinity chromatography. oxlthis was readily obtained in high purity (>/=95%) and reasonable yield (>/=60%), and showed kinetic and biochemical features characteristic of its parent, oxlt, including an unusually high maximal velocity (60 micromol/min per mg of protein at 4 degrees c). circular dichroism spectroscopy of purified oxlthis identified the al ... | 1997 | 8999913 |
| identification and classification of oxalobacter formigenes strains by using oligonucleotide probes and primers. | genomic dnas of various strains of oxalobacter formigenes were subjected to restriction endonuclease fragment length polymorphism- and pcr-based amplification analyses with dna probes and primers complementary to sequences within either the oxc gene, encoding oxalyl coenzyme a (oxalyl-coa) decarboxylase, or the frc gene, encoding formyl-coa transferase. oligonucleotide probes based on nonconserved sequences of oxc or frc were able to divide o. formigenes strains into at least two groups, consist ... | 1997 | 9003594 |
| dna sequencing and expression of the formyl coenzyme a transferase gene, frc, from oxalobacter formigenes. | oxalic acid, a highly toxic by-product of metabolism, is catabolized by a limited number of bacterial species utilizing an activation-decarboxylation reaction which yields formate and co2. frc, the gene encoding formyl coenzyme a transferase, an enzyme which transfers a coenzyme a moiety to activate oxalic acid, was cloned from the bacterium oxalobacter formigenes. dna sequencing revealed a single open reading frame of 1,284 bp capable of encoding a 428-amino-acid protein. a presumed promoter re ... | 1997 | 9150242 |
| structure-function relationships in oxlt, the oxalate/formate transporter of oxalobacter formigenes. topological features of transmembrane helix 11 as visualized by site-directed fluorescent labeling. | analysis of hydropathy suggests that in oxlt, the oxalate/formate antiporter of oxalobacter formigenes, lysine 355 is within transmembrane helix no. 11. to test this idea, we used single-cysteine, histidine-tagged oxlt variants to study the organization of a 30-residue segment (residues 344-373) containing this region. topology was examined by probing the a345c and a370c proteins with oregon green maleimide carboxylic acid, an impermeant and fluorescent thiol-reactive agent. examination of purif ... | 1998 | 9651403 |
| the lotus japonicus ljnod70 nodulin gene encodes a protein with similarities to transporters. | a novel nodule-specific gene, ljnod70, associated with late stages in lotus japonicus nodule development and/or functioning was characterized. the ljnod70 gene is a member of a small family of closely related l. japonicus genes. two major mrna species corresponding to the ljnod70 gene were identified in nodules and shown to be the result of a mechanism resembling alternative splicing. the longer, presumably unspliced, mrna species was shown to contain a single open reading frame (orf), encoding ... | 1998 | 9687069 |
| absence of oxalobacter formigenes in cystic fibrosis patients: a risk factor for hyperoxaluria. | patients with cystic fibrosis have an increased risk of hyperoxaluria, and of subsequent nephrocalcinosis and calcium-oxalate urolithiasis. oxalate homoeostasis is controlled, in part, by the intestinal bacterium, oxalobacter formigenes. the loss of this bacterium from the gut flora is associated with an increased risk of hyperoxaluria and calcium-oxalate urolithiasis. we investigated whether the absence of o. formigenes and the presence of hyperoxaluria are correlated in cystic fibrosis (cf) pa ... | 1998 | 9759746 |
| phylogenetic identification of two major nitrogen-fixing bacteria associated with sugarcane. | acetobacter diazotrophicus and herbaspirillum seropedicae were identified by genetic methods based on 16s rrna sequences. a specific pcr method in combination with probing was developed for a. diazotrophicus. the pcr system includes four primers, of which the primers named ac (ctgtttcccgcaagggac) and di (gcgccccattgctgggtt) generated an 445 bp amplicon in all of the 11 a. diazotrophicus strains tested. the phylogenetic position of h. seropedicae was determined. h. seropedicae forms with oxalobac ... | 1998 | 9924818 |
| direct quantification of the enteric bacterium oxalobacter formigenes in human fecal samples by quantitative competitive-template pcr. | homeostasis of oxalic acid appears to be regulated, in part, by the gut-associated bacterium oxalobacter formigenes. the loss of this bacterium from the gut flora is associated with an increased susceptibility to hyperoxaluria, a condition which can lead to the formation of calcium oxalate crystalluria and kidney stones. in order to identify and quantify the presence of o. formigenes in clinical specimens, a quantitative-pcr-based assay system utilizing a competitive dna template as an internal ... | 1999 | 10203513 |
| evaluating children in the ukraine for colonization with the intestinal bacterium oxalobacter formigenes, using a polymerase chain reaction-based detection system. | background: oxalobacter formigenes is a recently discovered anaerobic bacterium residing in the gastrointestinal tracts of most vertebrates, including humans. evidence suggests that this bacterium plays an important symbiotic relationship with its hosts by regulating oxalic acid homeostasis. oxalic acid is a ubiquitous toxic by-product of metabolism associated with numerous pathologic conditions, including hyperoxaluia, cardiac myopathy and conductance disorders, kidney stones, and even death. d ... | 1997 | 10462596 |
| direct correlation between hyperoxaluria/oxalate stone disease and the absence of the gastrointestinal tract-dwelling bacterium oxalobacter formigenes: possible prevention by gut recolonization or enzyme replacement therapy. | oxalobacter formigenes is a specific oxalate-degrading, anaerobic bacterium inhabiting the gastrointestinal tracts of vertebrates, including humans. this bacterium maintains an important symbiotic relationship with its host by regulating oxalate homeostasis, primarily by preventing enteric absorption. increased absorption of oxalate can lead to multiple complications associated with hyperoxaluria, especially recurrent calcium oxalate urolithiasis. detection of o. formigenes in the gastrointestin ... | 1999 | 10541258 |
| janthinobacterium agaricidamnosum sp. nov., a soft rot pathogen of agaricus bisporus. | a novel bacterium has been found that causes a soft rot disease of agaricus bisporus, the cultivated mushroom. it has been characterized using nutritional, physiological, chemical and molecular techniques. based on these data, it was shown to have many characteristics in common with members of the genus janthinobacterium. despite similarities to the only described species within this genus, janthinobacterium lividum, there were a number of differences between the mushroom pathogen isolated and t ... | 1999 | 10555339 |
| urinary oxalate excretion in urolithiasis and nephrocalcinosis. | to investigate urinary oxalate excretion in children with urolithiasis and/or nephrocalcinosis and to classify hyperoxaluria (hyox). | 2000 | 10735843 |
| oxalate-degrading enterococcus faecalis. | an oxalate-degrading enterococcus faecalis was isolated from human stools under anaerobic conditions. the bacteria required a poor nutritional environment and repeated subculturing to maintain their oxalate-degrading ability. the e. faecalis produced 3 proteins (65, 48, and 40 kda) that were not produced by non-oxalate-degrading e. faecalis as examined by sds-page. antibodies against oxalyl-coenzyme a decarboxylase (65 kda) and formyl-coenzyme a transferase (48 kda) obtained from oxalobacter for ... | 2000 | 10832966 |
| structure/function relationships in oxlt, the oxalate-formate transporter of oxalobacter formigenes. assignment of transmembrane helix 11 to the translocation pathway. | oxlt, the oxalate:formate antiporter of oxalobacter formigenes, has a lone charged residue, lysine 355 (lys-355), at the center of transmembrane helix 11 (tm11). because lys-355 is the only charged residue in the hydrophobic sector, we tested the hypothesis that lysine 355 contributes to the binding site for the anionic substrate, oxalate. this idea was supported by mutational analysis, which showed that of five variants studied (lys-355 --> cys, gly, gln, arg, or thr), residual function was fou ... | 2001 | 11113128 |
| topology of oxlt, the oxalate transporter of oxalobacter formigenes, determined by site-directed fluorescence labeling. | the topology of oxlt, the oxalate:formate exchange protein of oxalobacter formigenes, was established by site-directed fluorescence labeling, a simple strategy that generates topological information in the context of the intact protein. accessibility of cysteine to the fluorescent thiol-directed probe oregon green maleimide (ogm) was examined for a panel of 34 single-cysteine variants, each generated in a his(9)-tagged cysteine-less host. the reaction with ogm was readily scored by examining the ... | 2001 | 11274108 |
| helix proximity in oxlt, the oalate:formate antiporter of oxalobacter formigenes. cross-linking between tm2 and tm11. | experiments were designed to evaluate the proximity of transmembrane helices two (tm2) and eleven (tm11) in the tertiary structure of oxlt, the oxalate:formate exchange transporter of oxalobacter formigenes. a tandem duplication of the factor xa protease cleavage site (iegriegr) was inserted into the central cytoplasmic loop of an oxlt cysteine-less derivative in which an endogenous cleavage site had been eliminated by mutagenesis (r248q). using this host, double cysteine derivatives were constr ... | 2001 | 11457863 |
| projection structure and molecular architecture of oxlt, a bacterial membrane transporter. | the major facilitator superfamily (mfs) represents the largest collection of evolutionarily related members within the class of membrane 'carrier' proteins. oxlt, a representative example of the mfs, is an oxalate-transporting membrane protein in oxalobacter formigenes. from an electron crystallographic analysis of two-dimensional crystals of oxlt, we have determined the projection structure of this membrane transporter. the projection map at 6 a resolution indicates the presence of 12 transmemb ... | 2001 | 11500368 |
| reduction of oxaluria after an oral course of lactic acid bacteria at high concentration. | hyperoxaluria is a major risk factor for renal stones, and in most cases, it appears to be sustained by increased dietary load or increased intestinal absorption. previous studies have shown that components of the endogenous digestive microflora, in particular oxalobacter formigenes, utilize oxalate in the gut, thus limiting its absorption. we tested the hypothesis of whether oxaluria can be reduced by means of reducing intestinal absorption through feeding a mixture of freeze-dried lactic acid ... | 2001 | 11532105 |
| rapid reversal of hyperoxaluria in a rat model after probiotic administration of oxalobacter formigenes. | the gut inhabiting bacterium oxalobacter formigenes may be a negative risk factor in recurrent calcium oxalate kidney stone disease that apparently maintains oxalic acid homeostasis in its host via the degradation of dietary oxalate. the possibility of using this bacterium as probiotic treatment to reduce urinary oxalate was investigated in a rat model. | 2001 | 11547118 |
| involvement of coenzyme a esters and two new enzymes, an enoyl-coa hydratase and a coa-transferase, in the hydration of crotonobetaine to l-carnitine by escherichia coli. | two proteins (caib and caid) were found to catalyze the reversible biotransformation of crotonobetaine to l-carnitine in escherichia coli in the presence of a cosubstrate (e.g., gamma-butyrobetainyl-coa or crotonobetainyl-coa). caib (45 kda) and caid (27 kda) were purified in two steps to electrophoretic homogeneity from overexpression strains. caib was identified as crotonobetainyl-coa:carnitine coa-transferase by maldi-tof mass spectrometry and enzymatic assays. the enzyme exhibits high cosubs ... | 2001 | 11551212 |
| urinary oxalate excretion in female calcium oxalate stone formers with and without a history of recurrent urinary tract infections. | therapy with antibiotics in recurrent urinary tract infections may destroy colonies of oxalobacter formigenes in the intestinal tract. a lack of oxalate degradation caused by the absence of this bacterium is suggested to contribute to the hyperabsorption of dietary oxalate and to the increase in urinary oxalate excretion. the present study was performed to evaluate the effect of recurrent urinary tract infections and subsequent changes induced in the urinary excretion profile in female calcium o ... | 2001 | 11585279 |
| molecular identification of oxalobacter formigenes with the polymerase chain reaction in fresh or frozen fecal samples. | to develop a simple and rapid polymerase chain reaction (pcr) method for detecting oxalobacter formigenes (which degrades oxalate in the gut) in fecal specimens from healthy volunteers and patients with urolithiasis, and to determine whether o. formigenes can be detected in frozen or fresh fecal samples. | 2001 | 11678762 |
| structure/function relationships in oxlt, the oxalate/formate antiporter of oxalobacter formigenes: assignment of transmembrane helix 2 to the translocation pathway. | we constructed a single cysteine panel encompassing transmembrane helix two (tm2) of oxlt, the oxalate/formate antiporter of oxalobacter formigenes. among the 21 positions targeted, cysteine substitution identified one (phenylalanine 59) as essential to oxlt expression and three (glutamine 56, glutamine 66, and serine 69) as potentially critical to oxlt function. by probing membranes with a bulky hydrophilic probe (oregon green maleimide) we also located a central inaccessible core of at least e ... | 2002 | 11919184 |
| three-dimensional structure of a bacterial oxalate transporter. | the major facilitator superfamily (mfs) represents one of the largest classes of evolutionarily related membrane transporter proteins. here we present the three-dimensional structure at 6.5 a resolution of a bacterial member of this superfamily, oxlt. the structure, derived from an electron crystallographic analysis of two-dimensional crystals, reveals that the 12 helices in the oxlt molecule are arranged around a central cavity, which is widest at the center of the membrane. the helices divide ... | 2002 | 12118242 |
| oxalobacter formigenes and its potential role in human health. | oxalate degradation by the anaerobic bacterium oxalobacter formigenes is important for human health, helping to prevent hyperoxaluria and disorders such as the development of kidney stones. oxalate-degrading activity cannot be detected in the gut flora of some individuals, possibly because oxalobacter is susceptible to commonly used antimicrobials. here, clarithromycin, doxycycline, and some other antibiotics inhibited oxalate degradation by two human strains of o. formigenes. these strains vari ... | 2002 | 12147479 |
| detection and identification of oxalate-degrading bacteria in human feces. | oxalate is detoxified (catabolized) via the action of two enzymatic proteins, formyl coenzyme a transferase (encoded by the frc gene) and oxalyl coenzyme a decarboxylase (encoded by the oxc gene), contained in the cytosol of oxalobacter formigenes that colonizes the human intestinal tract. it is speculated that oxalate-degrading bacteria decrease oxalate absorption from the intestines and their absence in the gastrointestinal tract correlates with the formation of calcium-oxalate urolithiasis. | 2002 | 12165021 |
| role of oxalobacter formigenes in calcium oxalate stone disease: a study from north india. | the present study was performed to detect the presence of an oxalate degrading bacteria oxalobacter formigenes in the gi tract of calcium oxalate stone patients and normal individuals from north india. furthermore, the possible relationship of this bacterium with number of stone episodes in this part of the world was also studied. the correlation of the presence or absence of o. formigenes with the urinary oxalate levels was evaluated. | 2002 | 12180235 |
| adaptation to nickel spiking of bacterial communities in neocaledonian soils. | adaptation to nickel of bacterial communities of two extreme neocaledonian soils (an ultramafic soil and an acidic soil) was investigated by nickel spiking and compared with adaptation in a non-neocaledonian soil used as reference. soil microcosms were amended with nickel chloride (nicl2), and bacterial community structure was analysed with the ribosomal intergenic spacer analysis (risa) technique. then, bacterial populations that respond to nickel stress were identified by cloning and sequencin ... | 2003 | 12542708 |
| infections and urinary stone disease. | the relationship between urinary infections and stone formation has been recognized since antiquity and it has been over a century since bacterial degradation of urea was postulated to cause struvite stones. specific therapy for urease-producing bacteria, such as urease-inhibitors and antibiotics, has allowed for treatment for this subset of urinary stones. future directions for research include development of novel urease-inhibitors and chemicals to enhance the protective glycosaminoglycan laye ... | 2003 | 12678863 |
| medical management of stone disease. | dietary manipulation still remains one of the most important strategies for therapy. a growing body of evidence, however, suggests that severe calcium restriction is inappropriate in patients with recurrent nephrolithiasis. dietary recommendations based on recent evidence and the role of bacteria in the pathogenesis of calcium nephrolithiasis are discussed. | 2003 | 12692447 |
| probiotics and the urologist. | emerging from the stigma of once being referred to as "snake oil", excellent scientific and clinical evidence now exists to indicate that probiotics do indeed have a role to play in medicine. the proper definition of probiotics is important "live microorganisms which when administered in adequate amounts confer a health benefit on the host", for several reasons. it rules out so-called probiotics that have no clinically proven, peer-reviewed data, and it states the need to have viable bacteria pr ... | 2003 | 12773227 |
| intestinal oxalobacter formigenes colonization in calcium oxalate stone formers and its relation to urinary oxalate. | oxalobacter formigenes is an anaerobic commensal colonic bacterium capable of degrading oxalate through the enzyme oxalyl-coa decarboxylase. it has been theorized that individuals who lack this bacterium have higher intestinal oxalate absorption, leading to a higher urinary oxalate concentration and an increased risk of calcium oxalate urolithiasis. we performed a prospective, controlled study to evaluate o. formigenes colonization in calcium oxalate stone formers and to correlate colonization w ... | 2003 | 12803990 |
| molecular epidemiology of fecal oxalobacter formigenes in healthy adults living in seoul, korea. | oxalobacter formigenes is a member of the intestinal flora that degrades oxalate. this bacterium maintains an important symbiotic relation with its hosts by regulating oxalic acid absorption in the intestine as well as oxalic acid concentrations in plasma. we tried to define the prevalence of fecal o. formigenes positivity in healthy adults. | 2003 | 12816588 |
| the association of nephrolithiasis with cystic fibrosis. | there is a growing body of evidence regarding the association between cystic fibrosis (cf) and nephrolithiasis and the role that oxalobacter formigenes may have in that association. | 2003 | 12830451 |
| crystallization and preliminary crystallographic analysis of formyl-coa tranferase from oxalobacter formigenes. | formyl-coa transferase from oxalobacter formigenes has been expressed as a recombinant protein in escherichia coli and purified to homogeneity. crystals of formyl-coa transferase were grown at 293 k using polyethylene glycol 4000 as a precipitant. the diffraction pattern of flash-frozen crystals at 100 k extends to 2.2 a resolution with synchrotron radiation (lambda = 0.933 nm). the crystals are tetragonal and belong to space group i4, with unit-cell parameters a = b = 151.44, c = 99.49 a. the a ... | 2003 | 12832784 |
| formyl-coa transferase encloses the coa binding site at the interface of an interlocked dimer. | formyl-coa transferase catalyses transfer of coa from formate to oxalate in the first step of oxalate degradation by oxalobacter formigenes, a bacterium present in the intestinal flora which is implicated in oxalate catabolism in mammals. formyl-coa transferase is a member of a family of coa-transferases for which no structural information is available. we now report the three-dimensional structure of o.formigenes formyl-coa transferase, which reveals a novel fold and a very striking assembly of ... | 2003 | 12839984 |
| the crystal structure of the escherichia coli yfdw gene product reveals a new fold of two interlaced rings identifying a wide family of coa transferases. | because of its toxicity, oxalate accumulation from amino acid catabolism leads to acute disorders in mammals. gut microflora are therefore pivotal in maintaining a safe intestinal oxalate balance through oxalate degradation. oxalate catabolism was first identified in oxalobacter formigenes, a specialized, strictly anaerobic bacterium. oxalate degradation was found to be performed successively by two enzymes, a formyl-coa transferase (frc) and an oxalate decarboxylase (oxc). these two genes are p ... | 2003 | 12844490 |
| oxalate-degrading enzymes from oxalobacter formigenes: a novel device coating to reduce urinary tract biomaterial-related encrustation. | the long-term placement of biomaterials within the urinary tract is limited by the development of encrustation. in a noninfected urinary environment, encrustation often results from the deposition of calcium oxalate on the biomaterial surface. there is an association between the absence of oxalobacter formigenes, a commensal colonic bacterium capable of degrading oxalate, and calcium oxalate stone formation. this pilot study was designed to evaluate several oxalate-degrading enzymes produced by ... | 2003 | 12885351 |
| diagnostic and therapeutic approaches in patients with secondary hyperoxaluria. | secondary hyperoxaluria is due either to increased intestinal oxalate absorption or to excessive dietary oxalate intake. certain intestinal diseases like short bowel syndrome, chronic inflammatory bowel disease or cystic fibrosis and other malabsorption syndromes are known to increase the risk of secondary hyperoxaluria. although the urinary oxalate excretion is usually lower than in primary hyperoxaluria, it may still lead to significant morbidity by recurrent urolithiasis or progressive nephro ... | 2003 | 12957811 |
| stone composition, metabolic profile and the presence of the gut-inhabiting bacterium oxalobacter formigenes as risk factors for renal stone formation. | to examine stone composition, metabolic evaluation and colonization of oxalobacter formigenes as risk factors for renal stone formation. | 2003 | 12966191 |
| [detection of oxalobacter formigenes in human feces and study of related genes in a new oxalate-degrading bacterium]. | the first objective of the present study was to examine the presence of oxalobacter formigenes (an oxalate-degrading bacterium in the human intestine) according to sex in a large number of japanese. the second objective was to study the presence of three related genes in bifidobacterium breve, which is considered to be a new oxalate-degrading bacterim. fecal samples were collected from 55 male and 37 female healthy volunteers. o. formigenes was detected by a polymerase chain reaction (pcr) and a ... | 2003 | 12968475 |
| urinary oxalate levels and the enteric bacterium oxalobacter formigenes in patients with calcium oxalate urolithiasis. | we performed a prospective study to evaluate the intestinal colonization of oxalobacter formigenes and its relationship with urinary oxalate levels in patients with calcium oxalate stone disease. | 2003 | 14499684 |
| role of oxalobacter formigenes in calcium oxalate stone disease: a study from north india. | 2003 | 14601587 | |
| projection structure of the bacterial oxalate transporter oxlt at 3.4a resolution. | oxlt is a bacterial transporter protein with 12 transmembrane segments that belongs to the major facilitator superfamily of transporters. it facilitates the exchange of oxalate and formate across the membrane of the gram-negative bacterium oxalobacter formigenes. from an electron crystallographic analysis of two-dimensional, tube-like crystals of oxlt, we have previously determined the three-dimensional structure of this transporter at 6.5 a resolution. here, we report conditions to obtain cryst ... | 2003 | 14643200 |
| oxalobacter formigenes and its role in oxalate metabolism in the human gut. | oxalate is ingested in a wide range of animal feeds and human foods and beverages and is formed endogenously as a waste product of metabolism. bacterial, rather than host, enzymes are required for the intestinal degradation of oxalate in man and mammals. the bacterium primarily responsible is the strict anaerobe oxalobacter formigenes. in humans, this organism is found in the colon. o. formigenes has an obligate requirement for oxalate as a source of energy and cell carbon. in o. formigenes, the ... | 2004 | 14734158 |
| colonization of the neonatal rat intestinal tract from environmental exposure to the anaerobic bacterium oxalobacter formigenes. | oxalobacter formigenes, an anaerobic bacterium that inhabits the mammalian gastrointestinal tract, has an important symbiotic relationship with its vertebrate hosts by regulating oxalic acid homeostasis. epidemiological studies of o. formigenes colonization in man have shown that colonization occurs in young children, that every child can become colonized naturally, that >20% lose colonization during adolescence or as adults and that stable colonization can be disrupted by antibiotic use or chan ... | 2004 | 14970252 |
| kinetic and mechanistic characterization of the formyl-coa transferase from oxalobacter formigenes. | oxalobacter formigenes is an obligate anaerobe that colonizes the human gastrointestinal tract and employs oxalate breakdown to generate atp in a novel process involving the interplay of two coupled enzymes and a membrane-bound oxalate:formate antiporter. formyl-coa transferase is a critical enzyme in oxalate-dependent atp synthesis and is the first class iii coa-transferase for which a high resolution, three-dimensional structure has been determined (ricagno, s., jonsson, s., richards, n., and ... | 2004 | 15213226 |
| gut-inhabiting bacterium oxalobacter formigenes: role in calcium oxalate urolithiasis. | oxalate plays a crucial role in the formation of most renal stones. oxalate is a common constituent of most diets and a byproduct of metabolism, and if it is not sufficiently degraded, it may accumulate. in humans, gut bacteria degrade 70 to 100 mg of oxalate per day. oxalobacter formigenes is a gram-negative, obligately anaerobic, rod-shaped bacterium with an absolute requirement for oxalate. although not present in the gut at birth, it quickly colonizes most children, and there is epidemiologi ... | 2004 | 15253809 |
| structure and transport mechanism of the bacterial oxalate transporter oxlt. | membrane proteins that belong to the major facilitator superfamily (mfs) are found in organisms across the evolutionary spectrum and mediate the transport of a variety of substrates ranging from small metabolites to neurotransmitters. the oxalate transporter (oxlt) is a representative mfs protein, and exchanges formate for oxalate across the cytoplasmic membrane of the organism oxalobacter formigenes. here, we present a structural model for the protein conformational changes that occur during ox ... | 2004 | 15339805 |
| characterization and heterologous expression of the oxalyl coenzyme a decarboxylase gene from bifidobacterium lactis. | oxalyl coenzyme a (coa) decarboxylase (oxc) is a key enzyme in the catabolism of the highly toxic compound oxalate, catalyzing the decarboxylation of oxalyl-coa to formyl-coa. the gene encoding a novel oxalyl-coa decarboxylase from bifidobacterium lactis dsm 10140 (oxc) was identified and characterized. this strain, isolated from yogurt, showed the highest oxalate-degrading activity in a preliminary screening with 12 strains belonging to bifidobacterium, an anaerobic intestinal bacterial group l ... | 2004 | 15345383 |
| [future perspective on the prevention of nephrolithiasis]. | renal stone formation has been explained by the physicochemical theory; i.e., nucleation, growth and aggregation of crystals in the urine. current medical prevention is based on this theory and seeks to modulate promoters and inhibitors of stone formation. recent studies have identified increasing numbers of macromolecular inhibitors such as glycosaminoglycans, bikunin, osteopontin and urinary prothrombin f1. these appear to be more important than low-molecular inhibitors like citrate. on the ot ... | 2004 | 15471083 |
| microorganisms and calcium oxalate stone disease. | microorganisms may have a role in the pathogenesis and prevention of kidney stones. the subjects of this review include nanobacteria, oxalobacter formigenes, and lactic acid bacteria. not reviewed here is the well-described role of infections of the urinary tract with proteus species and other urease-producing organisms associated with struvite stone formation. nanobacteria have been proposed to be very small (0.08-0.5 nm), ubiquitous organisms that could play a role in stone formation. the theo ... | 2004 | 15499215 |
| role of dietary intake and intestinal absorption of oxalate in calcium stone formation. | the factors affecting the urinary excretion of oxalate are critical to the risk of forming calcium oxalate stones. this article reviews the role of dietary and intestinal oxalate in determining the level of oxalate excreted in urine. the amount of oxalate available for absorption throughout the intestine is highly dependent on the state of oxalate (a) in the food ingested, and (b) in the intestinal contents at each section of the intestinal tract since only the soluble form of oxalate can be abs ... | 2004 | 15499217 |
| intestinal transport of an obdurate anion: oxalate. | in this review, we focus on the role of gastrointestinal transport of oxalate primarily from a contemporary physiological standpoint with an emphasis on those aspects that we believe may be most important in efforts to mitigate the untoward effects of oxalate. included in this review is a general discussion of intestinal solute transport as it relates to oxalate, considering cellular and paracellular avenues, the transport mechanisms, and the molecular identities of oxalate transporters. in addi ... | 2005 | 15565438 |
| infrequency of colonization with oxalobacter formigenes in inflammatory bowel disease: possible role in renal stone formation. | calcium oxalate renal stones (rs) and hyperoxaluria are common in patients with inflammatory bowel disease (ibd). the absence of intestinal oxalate degrading bacteria, oxalobacter formigenes, may cause hyperoxaluria in ibd. the aim of the present study was to examine: (i) the colonization of o. formigenes in patients with ibd and controls and to correlate its presence with urinary oxalate excretion; and (ii) urinary analytes contributing to rs in ibd. | 2004 | 15610315 |
| bacterial community composition determined by culture-independent and -dependent methods during propane-stimulated bioremediation in trichloroethene-contaminated groundwater. | an in situ co-metabolic air sparging (cas) study was carried out at mcclellan air force base (mafb), sacramento, ca, usa, in a trichloroethene- (tce) and cis-dichloroethene (cis-dce)-contaminated aquifer where one test zone received 2% propane in air and the other served as a control and received only air. as part of that study, bacterial population shifts were evaluated by length heterogeneity polymerase chain reaction (lh-pcr). the results showed that an organism(s) that had a fragment size of ... | 2005 | 15658984 |
| effect of antibiotics on oxalobacter formigenes colonization of human gastrointestinal tract. | oxalobacter formigenes is a bacterium residing in the human gastrointestinal tract that degrades oxalate and reduces its availability for absorption. this bacterium is assumed to be antibiotic sensitive, and repeated antibiotic therapies could eradicate it. the aim of the present study was to determine the differences in the colonization by o. formigenes of individuals who had been on antibiotics for at least 5 days at the time of sample collection and individuals who had not taken antibiotics f ... | 2005 | 15735393 |
| crystal structure of escherichia coli crotonobetainyl-coa: carnitine coa-transferase (caib) and its complexes with coa and carnitinyl-coa. | l-carnitine (r-[-]-3-hydroxy-4-trimethylaminobutyrate) is found in both eukaryotic and prokaryotic cells and participates in diverse processes including long-chain fatty-acid transport and osmoprotection. the enzyme crotonobetainyl/gamma-butyrobetainyl-coa:carnitine coa-transferase (caib; e.c. 2.8.3.-) catalyzes the first step in carnitine metabolism, leading to the final product gamma-butyrobetaine. the crystal structures of escherichia coli apo-caib, as well as its asp169ala mutant bound to co ... | 2005 | 15823031 |
| experimental tests of a homology model for oxlt, the oxalate transporter of oxalobacter formigenes. | using the x-ray structure of the glycerol 3-phosphate transporter (glpt), we devised a model for the distantly related oxalate transporter, oxlt. the model accommodates all earlier biochemical information on oxlt, including the idea that lys-355 lies on the permeation pathway, and predicts that lys-355 and a second positive center, arg-272, comprise the binding site for divalent oxalate. study of r272k, r272a, and r272q derivatives verifies that arg-272 is essential, and comparisons with glpt sh ... | 2005 | 15932938 |
| oxalate-degrading providencia rettgeri isolated from human stools. | oxalate-degrading bacteria are thought to metabolize intestinal oxalate and thus decrease the urinary excretion of oxalate by reducing its intestinal absorption. | 2005 | 15985073 |
| absorptive hyperoxaluria leads to an increased risk for urolithiasis or nephrocalcinosis in cystic fibrosis. | hyperoxaluria has been incriminated to account for the increased incidence of urolithiasis or nephrocalcinosis in patients with cystic fibrosis (cf). hyperoxaluria presumably is caused by fat malabsorption and the absence of such intestinal oxalate-degrading bacteria as oxalobacter formigenes. to better elucidate its pathophysiological characteristics, we prospectively studied patients with cf by determining these parameters and performing renal ultrasonography twice yearly. | 2005 | 16129205 |
| detection and characterization of merohedral twinning in crystals of oxalyl-coenzyme a decarboxylase from oxalobacter formigenes. | oxalyl-coenzyme a decarboxylase is a thiamin diphosphate dependent enzyme active in the catabolism of the highly toxic compound oxalate. the enzyme from oxalobacter formigenes has been expressed as a recombinant protein in escherichia coli, purified to homogeneity and crystallized. two crystal forms were obtained, one showing poor diffraction and the other merohedral twinning. crystals in the former category belong to the tetragonal space group p4(2)2(1)2. data to 4.1 a resolution were collected ... | 2006 | 16198641 |
| structural basis for activation of the thiamin diphosphate-dependent enzyme oxalyl-coa decarboxylase by adenosine diphosphate. | oxalyl-coenzyme a decarboxylase is a thiamin diphosphate-dependent enzyme that plays an important role in the catabolism of the highly toxic compound oxalate. we have determined the crystal structure of the enzyme from oxalobacter formigenes from a hemihedrally twinned crystal to 1.73 a resolution and characterized the steady-state kinetic behavior of the decarboxylase. the monomer of the tetrameric enzyme consists of three alpha/beta-type domains, commonly seen in this class of enzymes, and the ... | 2005 | 16216870 |
| oxalate degrading bacteria: new treatment option for patients with primary and secondary hyperoxaluria? | current treatment options in patients with primary and secondary hyperoxaluria are limited and do not always lead to sufficient reduction in urinary oxalate excretion. intestinal oxalate degrading bacteria are capable of degrading oxalate to co(2) and formate, the latter being further metabolized and excreted via the feces. it is speculated, that both endogenously produced, as well as dietary oxalate can be significantly removed via the intestinal tract. oxalobacter formigenes, an obligate anaer ... | 2005 | 16284877 |
| an animal model of calcium oxalate urolithiasis based on a cyclooxygenase 2 selective inhibitor. | our aim was to develop a stone-forming animal model involving renal tubular injury using a cyclooxygenase 2 selective inhibitor. male sprague-dawley rats fed chow containing 3% sodium oxalate with or without 100 mg/kg celecoxib were compared to animals fed normal chow. rats were killed after 2 or 4 weeks and the kidneys were harvested for morphological examination. collections of 24-h urine were made before kidney harvest. after 2 weeks only a few crystals were observed in rats that received oxa ... | 2005 | 16311770 |
| oxalobacter sp. reduces urinary oxalate excretion by promoting enteric oxalate secretion. | the primary goal of this study was to test the hypothesis that oxalobacter colonization alters colonic oxalate transport thereby reducing urinary oxalate excretion. in addition, we examined the effects of intraluminal calcium on oxalobacter colonization and tested the hypothesis that endogenously derived colonic oxalate could be degraded by lyophilized oxalobacter enzymes targeted to this segment of the alimentary tract. oxalate fluxes were measured across short-circuited, in vitro preparations ... | 2006 | 16518326 |
| anabolic incorporation of oxalate by oxalobacter formigenes. | cell-free lysates of the strict anaerobe oxalobacter formigenes contained the following enzymatic activities: oxalyl coenzyme a reductase, glyoxylate carboligase, tartronic semialdehyde reductase, and glycerate kinase. nad(p)-linked formate dehydrogenase, serine-glyoxylate aminotransferase, and nad(p) transhydrogenase activities were not detected. these results support the hypothesis that o. formigenes assimilates carbon from oxalate by using the glycerate pathway, whereby oxalate is reduced to ... | 1996 | 16535386 |
| oxalobacter formigenes: a potential tool for the treatment of primary hyperoxaluria type 1. | primary hyperoxaluria is characterized by severe urolithiasis, nephrocalcinosis, and early renal failure. as treatment options are scarce, we aimed for a new therapeutic tool using colonic degradation of endogenous oxalate by oxalobactor formigenes. oxalobacter was orally administered for 4 weeks as frozen paste (ixoc-2) or as enteric-coated capsules (ixoc-3). nine patients (five with normal renal function, one after liver-kidney transplantation, and three with renal failure) completed the ixoc- ... | 2006 | 16850020 |
| analysis of substrate-binding elements in oxlt, the oxalate:formate antiporter of oxalobacter formigenes. | an oxlt homology model suggests r272 and k355 in transmembrane helices 8 and 11, respectively, are critical to oxlt-mediated transport. we offer positive evidence supporting this idea by studying oxlt function after cysteine residues were separately introduced at these positions. without further treatment, both mutant proteins had a null phenotype when they were reconstituted into proteoliposomes. by contrast, significant recovery of function occurred when proteoliposomes were treated with mtsea ... | 2006 | 16922510 |
| treatment of the primary hyperoxalurias: a new chapter. | despite advances in the enzymology, molecular genetics, and clinical knowledge of the primary hyperoxalurias, few treatments are available. oxalobacter formigenes is a promising new therapy with potential to induce secretion of oxalate into the intestinal lumen, where it can be degraded by the bacteria. | 2006 | 16988727 |
| [effect of oral lactosucrose supplementation on human enteric oxalate-degrading bacteria]. | a variety of oxalate-degrading bacteria including oxalobacter formigenes and some species of bifidobacterium are known to colonize the human intestinal tract. oral lactosucrose supplementation promotes the growth of bifidobacterium in the human intestine. therefore, we investigated the effect of oral lactosucrose supplementation on enteric oxalate-degrading bacteria in twelve healthy men (age ranging from 25 to 39 years). lactosucrose was orally administered 10 g daily for 2 weeks without restri ... | 2006 | 17040052 |
| cloning and identification of frc gene from oxalobacter frmigenes. | the cloning and identification of frc gene from oxalobacter formigenes in the intestines of chinese people were conducted. the genomic dna of oxalobacter formigenes was extracted. frc gene fragment was amplified by polymerase chain reaction (pcr) and linked with pegfp-c1. the recombinant plasmid was designated pegfp-frc and was identified by restriction-enzyme digestion and sequencing. human embryo kidney 293 cells were transfected with pegfp-frc, then rt-pcr and western blotting were performed ... | 2007 | 17497294 |
| determination of oxalyl-coenzyme a decarboxylase activity in oxalobacter formigenes and lactobacillus acidophilus by capillary electrophoresis. | oxalyl-coenzyme a decarboxylase (oxc) is a key enzyme in the catabolism of the highly toxic oxalate, catalysing the decarboxylation of oxalyl-coenzyme a (ox-coa) to formyl-coenzyme a (for-coa). in the present study, a capillary electrophoretic (ce) method was proposed for the assessment of the activity of recombinant oxc from two bacteria, namely oxalobacter formigenes dsm 4420 and lactobacillus acidophilus la 14. in particular, the degradation of the substrate ox-coa occurring in the enzymatic ... | 2007 | 17499563 |
| hyperoxaluria, hypocitraturia, hypomagnesiuria, and lack of intestinal colonization by oxalobacter formigenes in a cervical spinal cord injury patient with suprapubic cystostomy, short bowel, and nephrolithiasis. | although urolithiasis is common in spinal cord injury patients, it is presumed that the predisposing factors for urinary stones in spinal cord injury patients are immobilization-induced hypercalciuria in the initial period after spinal injury and, in later stages, urine infection by urease-producing micro-organisms, e.g., proteus sp., which cause struvite stones. we describe a patient who sustained c-7 complete tetraplegia in a road traffic accident in 1970, when he was 16 years old. left ureter ... | 2006 | 17619709 |
| [metaphylaxis of recurrent renal calcium stones]. | calcium containing renal stones represent a common medical problem and show a high rate of recurrence. therefore, besides the treatment of acute stone episodes, also the prevention of new stone episodes is of crucial importance in the medical care of stone formers. to avoid stone recurrences, medical as well as dietary measures should be established based on the results of a thorough evaluation and the elaboration of an individual risk profile. this review article describes and discusses the cur ... | 2007 | 17685083 |
| stable expression of the oxc and frc genes from oxalobacter formigenes in human embryo kidney 293 cells: implications for gene therapy of hyperoxaluria. | hyperoxaluria can lead to multiple pathologic conditions such as recurrent urolithiasis, oxalosis, nephrocalcinosis and even renal failure, but there is no known oxalate-degrading pathway in the human body, and current therapeutic options for patients with hyperoxaluria are limited. oxalyl-coa decarboxylase and formyl-coa transferase are the key enzymes in the oxalate catabolism of oxalobacter formigenes which dwell in the intestine of vertebrates and have an important symbiotic relationship wit ... | 2007 | 17786282 |
| variability of oxalobacter formigenes and oxalate in stool samples. | the intestinal organism oxalobacter formigenes is unique in using oxalate as its primary carbon and energy source. intestinal colonization with o. formigenes may have clinical significance by decreasing intestinal oxalate and its absorption, thereby influencing the concentration of oxalate in plasma and urine, and the development of calcium oxalate stone disease. because the oxalate content of the diet varies considerably, we hypothesized that the number of o. formigenes and amount of oxalate wo ... | 2007 | 17870112 |
| reinvestigation of the catalytic mechanism of formyl-coa transferase, a class iii coa-transferase. | formyl-coenzyme a transferase from oxalobacter formigenes belongs to the class iii coenzyme a transferase family and catalyzes the reversible transfer of a coa carrier between formyl-coa and oxalate, forming oxalyl-coa and formate. formyl-coa transferase has a unique three-dimensional fold composed of two interlaced subunits locked together like rings of a chain. we here present an intermediate in the reaction, formyl-coa transferase containing the covalent beta-aspartyl-coa thioester, adopting ... | 2008 | 18162462 |
| oxalate balance in fat sand rats feeding on high and low calcium diets. | oxalate reduces calcium availability of food because it chelates calcium, forming the sparingly soluble salt calcium-oxalate. nevertheless, fat sand rats (psammomys obesus; gerbillinae) feed exclusively on plants containing much oxalate. we measured the effects of calcium intake on oxalate balance by comparing oxalate intake and excretion in wild fat sand rats feeding on their natural, oxalate-rich, calcium-poor diet with commercially-bred fat sand rats feeding on an artificial, calcium-rich, ox ... | 2008 | 18210126 |
| differential substrate specificity and kinetic behavior of escherichia coli yfdw and oxalobacter formigenes formyl coenzyme a transferase. | the yfdxwuve operon appears to encode proteins that enhance the ability of escherichia coli mg1655 to survive under acidic conditions. although the molecular mechanisms underlying this phenotypic behavior remain to be elucidated, findings from structural genomic studies have shown that the structure of yfdw, the protein encoded by the yfdw gene, is homologous to that of the enzyme that mediates oxalate catabolism in the obligate anaerobe oxalobacter formigenes, o. formigenes formyl coenzyme a tr ... | 2008 | 18245280 |
| oxalobacter formigenes may reduce the risk of calcium oxalate kidney stones. | most kidney stones are composed primarily of calcium oxalate. oxalobacter formigenes is a gram-negative, anaerobic bacterium that metabolizes oxalate in the intestinal tract and is present in a large proportion of the normal adult population. it was hypothesized that the absence of o. formigenes could lead to increased colonic absorption of oxalate, and the subsequent increase in urinary oxalate could favor the development of stones. to test this hypothesis, a case-control study involving 247 ad ... | 2008 | 18322162 |
| the roles and mechanisms of intestinal oxalate transport in oxalate homeostasis. | the mammalian intestine has an important role in the dynamics of oxalate exchange and thereby is significant in the etiology of calcium oxalate nephrolithiasis. here we review some of the phenomenologic observations that have led to the conclusion that anion exchangers (antiporters) are important mediators of secondarily active, net oxalate transport along the intestine (both absorptive and secretory). understanding the mechanisms of transepithelial oxalate transport has been advanced radically ... | 2008 | 18359395 |
| cysteine scanning mutagenesis of tm5 reveals conformational changes in oxlt, the oxalate transporter of oxalobacter formigenes. | we constructed a single-cysteine panel encompassing tm5 of the oxalate transporter, oxlt. the 25 positions encompassed by tm5 were largely tolerant of mutagenesis, and functional product was recovered for 21 of the derived variants. for these derivatives, thiol-directed mts-linked agents (mtsea, mtsce, and mtses) were used as probes of transporter function, yielding 11 mutants that responded to probe treatment, as indicated by effects on oxalate transport. further study identified three biochemi ... | 2008 | 18452311 |
| projection structure of a member of the amino acid/polyamine/organocation transporter superfamily. | the l-arginine/agmatine antiporter adic is a key component of the arginine-dependent extreme acid resistance system of escherichia coli. phylogenetic analysis indicated that adic belongs to the amino acid/polyamine/organocation (apc) transporter superfamily having sequence identities of 15-17% to eukaryotic and human apc transporters. for functional and structural characterization, we cloned, overexpressed, and purified wild-type adic and the point mutant adic-w293l, which is unable to bind and ... | 2008 | 18819925 |