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At least 19 recordsLinked to original sources
PubMed1993

Substrate and cofactor reactivity of a carbon monoxide dehydrogenase-corrinoid enzyme complex: stepwise reduction of iron-sulfur and corrinoid centers, the corrinoid Co2+/1+ redox midpoint potential, and overall synthesis of acetyl-CoA.

Cleavage of the acetyl carbon-carbon bond of acetyl-CoA in Methanosarcina barkeri is catalyzed by a high molecular mass multienzyme complex. The complex contains a corrinoid protein and carbon monoxide dehydrogenase and requires tetrahydrosarcinapterin (H4SPt) as methyl group acceptor. Reactions of the enzyme complex with carbon monoxide and with the methyl group donor N5-methyltetrahydrosarcinapterin (CH3-H4SPt) have been analyzed by UV-visible spectroscopy. Reduction of the enzyme complex by CO occurred in two steps. In the first step, difference spectra exhibited peaks of maximal absorbance decrease at 426 nm (major) and 324 nm (minor), characteristic of Fe-S cluster reduction. In the second step, corrinoid reduction to the Co1+ level was indicated by a prominent peak of increased absorbance at 394 nm. Spectrophotometric analyses of the corrinoid redox state were performed on the intact complex at potentials poised by equilibration with gas mixtures containing different [CO2]/[CO] ratios or by variation of the [H+]/[H2] ratio. The corrinoid Co2+/1+ midpoint potential was -426 mV (+/- 4 mV, n = 1.16 electrons, 24 degrees C), independent of pH (pH 6.4-8.0). The results indicated a significant fraction of Co1+ corrinoid at potentials existing in vivo. The reduced corrinoid reacted very rapidly with CH3-H4SPt. Reaction with methyl iodide was slow, and methylation by S-adenosylmethionine was not observed. Tne rate of methyl group transfer from CH3-H4SPt greatly exceeded the rate of CO reduction of enzyme centers. The enzyme complex catalyzed efficient synthesis of acetyl-CoA from coenzyme A, CO, and CH3-H4SPt. During acetyl-CoA synthesis, demethylation of CH3-H4SPt was monitored by the absorbance increase at 312 nm.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetyl Coenzyme A↗
PubMedDate not supplied

[Coalpha/Cobeta-isomerism of corrinoids. Partial synthesis and Escherichia coli activity of further isomer pairs of the (Co-methyl)-corrinoids (author's transl)].

In 2-methyladenyl-(Cobeta-methyl)-cobamide and in adenyl-(cobeta-methyl)-cobamide the nucleotide base is coordinated to the cobalt atom in neutral and weak acidic aqueous solutions (in the corresponding adenosylcorrinoids the nucleotide base is not coordinated). 2-Methylthioadenyl-(Cobeta-methyl)-cobamide resembles, with regard to the coordination of the nucleotide base, the benzimidazole-corrinoids. The partial synthesis via cobalt (I) corrinoids results in a variable proportion: (Coalpha-methyl) isomer/(Cobeta-methyl) isomer, e. g. 7/93 (cobalamin) and 50/50 (p-cresylcobamide). This proportion is generally low, if in the corresponding cyanocorrinoid the nucleotide base is firmly coordinated; it is high, if the coordination in the corresponding cyanocorrinoid is weak or absent. These results are compatible with the assumption that in the cobalt (I) corrinoids the nucleotide base is to a certain extent coordinated. In Escherichia coli 113-3 the examined (Coalpha-methyl)-corrinoids show a weaker bioactivity than the corresponding (Cobeta-methyl)-corrinoids.

Cobalt↗
PubMed1997

Diastereomeric Control in the Formation of Carbon-Cobalt Bonds in Organocobalt Corrinoids: Reactions of Cobalt(II) Corrinoids with Organic Hydroperoxides(1).

1,1-Dimethylpropyl hydroperoxide reacts with cobalt(II) cobinamide via a Fenton-like reaction to produce a mixture of the diastereomeric alpha- and beta-ethylcobinamides (CH(3)CH(2)Cbi(+)'s, in which the organic ligand is in the "lower" or "upper" axial ligand position, respectively), the composition of which depends on the ratio of starting materials. When the hydroperoxide reagent is in excess, <2% of the CH(3)CH(2)Cbi(+) product is the alpha diastereomer, a product distribution which agrees with previous observations of the equilibrium mixture. This distribution apparently arises because the previously demonstrated CH(3)CH(2)(*)-promoted isomerization of CH(3)CH(2)Cbi(+) diastereomers leads to equilibration. However, when cob(II)inamide is in excess over hydroperoxide, the CH(3)CH(2)Cbi(+) product contains 87% alpha diastereomer and 13% beta diastereomer. Evidently, under these conditions, trapping of the CH(3)CH(2)(*) radical is sufficiently rapid to prevent the radical-induced isomerization of diastereomers and a kinetically controlled product distribution results. This condition has been used to study the relative energetics of kinetically controlled alpha and beta alkylation of cob(II)inamide by CH(3)CH(2)(*). For cob(II)inamide itself, the alpha diastereomer is enthalpically stabilized relative to the beta diastereomer in the transition state for carbon-cobalt bond formation, but an even larger entropic stabilization of the beta diastereomer causes the latter to be the predominant product. The entropic preference for the beta diastereomer is shown to be the result of the differential side chain configurations at the alpha and beta faces of the cobalt corrinoids by experiments with side-chain-altered analogs. When the downwardly projecting f side chain is enlarged by esterification of the N-methylated nucleotide 1-alpha-D-ribofuranosyl-3,5,6-trimethylbenzimidazole 3'-phosphate, the proportion of the alpha diastereomer in the alkylated product drops to 74% and the effect is due solely to an increased entropic preference for the beta diastereomer. Similarly, when the normally downwardly projecting e propionamide side chain is epimerized to the upward (beta) face of the corrin, the proportion of the alpha diastereomer in the product is increased to 95% and the effect is entirely entropic again. Taken together with previous work, the results lead to a general picture of the energetics of alkyl radical + cobalt(II) corrinoid combination reactions and their microscopic reverse, the homolytic dissociation of carbon-cobalt bonds, a rare instance in which the subtleties of such diastereomeric control can be understood at a very fundamental level.

Journal Article↗
PubMed1988

Purification and some properties of the corrinoid-containing membrane protein from Methanobacterium thermoautotrophicum.

The cytoplasmic membrane of the methanogenic archaebacterium Methanobacterium thermoautotrophicum does not contain cytochromes, but did contain a corrinoid protein of molecular mass about 33 kDa which, after treatment with 10 mg Triton X-100/mg protein, was contained in a protein complex of about 500 kDa. Washed membranes from 1 g dry cells contained about 70 nmol of the cobamide factor III (5-hydroxybenzimidazolyl cobamide) as the sole corrinoid. The corrinoid-containing protein complex was purified and some of its properties were studied. According to several criteria it is an integral membrane protein complex. The corrinoid-protein complex, after about 100-fold purification, gave a single band on native PAGE and still had molecular mass of about 500 kDa. In SDS-PAGE several subunits were observed: in addition to the corrinoid-carrying subunit of about 33 kDa, other polypeptides of approximately 28 kDa, 26 kDa, and possibly 23 kDa were present. One mole of the purified 500-kDa protein complex contained greater than or equal to eight moles of the cobamide factor III. It was estimated that the corrinoid-protein complex accounts for 8% of the membrane protein of M. thermoautotrophicum. The visible spectrum of the oxidized protein exhibited absorbance maxima at 547 nm, 511 nm, and a shoulder at 468 nm, which disappeared upon reduction with dithionite. The midpoint potential of this transition was around -145 mV (pH 7). With EPR a Co2+ signal was observed within -50 mV and -350 mV with a maximum around -200 mV. Possible reasons for the disappearance of the Co2+ signal at low redox potentials are discussed. The line shape of the Co2+ signal was similar to that of Co2+ in free corrinoids. The signal of Co2+ could also be evoked by reduction with 5 mM dithiothreitol. From the redox properties of the corrinoid membrane protein it may be expected that in vivo the cobalt may become reduced and reoxidized. Its possible function as an electron-mediating membrane protein in the metabolism of methanogenic bacteria is discussed.

Bacterial Proteins↗
PubMed1991

Portal and biliary phases of enterohepatic circulation of corrinoids in humans.

The assimilation of labeled cobalamin and the transport of corrinoids in portal blood, peripheral venous blood, and bile were studied in eight cholecystectomized patients, after ingestion of a dose of cyano[57Co]cobalamin (0.5 microCi). The radioactivity appeared in the portal vein after a delay of 1.5-2 hours and in the peripheral vein 1 hour later. In bile, it reached a maximum at 24-72 hours; the excreted cobalamin corresponded to 1.42% +/- 0.92% of the dose ingested. The output of total corrinoids was 1.85 nmol/day. The high-performance liquid chromatography analysis of bile showed the presence of methylcobalamin, 5'-deoxyadenosylcobalamin, hydroxocobalamin, and an unknown corrinoid. This corrinoid bound to R binder but not to the intrinsic factor, and it had the same retention time as cobinamide. The R binder was the single cobalamin-binding protein found in bile. It was completely saturated in some periods of bile secretion. The corrinoids corresponding to such a period were eluted in Sephacryl S 300 gel filtration (Pharmacia Fine Chemicals, Uppsala, Sweden) in two peaks corresponding to saturated R binder and to free cobalamin. The mean level of total corrinoid was significantly higher in the portal vein (593 +/- 238 pmol/L) than in the peripheral vein (376 +/- 114 pmol/L) (P less than 0.01). This "cobalamin analogue" fraction was hypothetical because it was calculated from the difference between total corrinoid concentration and the so called "true cobalamin" concentration. This difference corresponded to the cobalamin analogue fraction. These data show that bile removes not only cobalamin but also cobalamin analogues and that R binder is the single carrier protein involved in their excretion.

Aged↗
PubMed2001

Isolation and characterization of a veratrol:corrinoid protein methyl transferase from Acetobacterium dehalogenans.

From 3-methoxyphenol-grown cells of Acetobacterium dehalogenans, an inducible enzyme was purified that mediated the transfer of the methyl groups of veratrol (1,2-dimethoxybenzene) to a corrinoid protein enriched from the same cells. In this reaction, veratrol was converted via 2-methoxyphenol to 1,2-dihydroxybenzene. The veratrol:corrinoid protein methyl transferase, designated MTIver, had an apparent molecular mass of about 32 kDa. With respect to the N-terminal amino acid sequence and other characteristics, MTIver is different from the vanillate:corrinoid protein methyl transferase (MTIvan) isolated earlier from the same bacterium. For the methyl transfer from veratrol to tetrahydrofolate, two additional protein fractions were required, one of which contained a corrinoid protein. This protein was not identical with the corrinoid protein of the vanillate O-demethylase system. However, the latter corrinoid protein could also serve as methyl acceptor for the veratrol:corrinoid protein methyl transferase. MTIver catalyzed the demethylation of veratrol, 3,4-dimethoxybenzoate, 2-methoxyphenol, and 3-methoxyphenol. Vanillate (3-methoxy-4-hydroxybenzoate), 2-methoxybenzoate, or 4-methoxybenzoate could not serve as substrates.

Acetobacter↗
PubMed1998

O-demethylase from Acetobacterium dehalogenans--cloning, sequencing, and active expression of the gene encoding the corrinoid protein.

The ether-cleaving O-demethylase from the strictly anaerobic homoacetogen Acetobacterium dehalogenans catalyses the methyltransfer from 4-hydroxy-3-methoxy-benzoate (vanillate) to tetrahydrofolate. In the first step a vanillate :corrinoid protein methyltransferase (methyltransferase I) mediates the methylation of a 25-kDa corrinoid protein with the cofactor reduced to cob(I)alamin. The methyl group is then transferred to tetrahydrofolate by the action of a methylcorrinoid protein:tetrahydrofolate methyltransferase (methyltransferase II). Using primers derived from the amino-terminal sequences of the corrinoid protein and the vanillate:corrinoid protein methyltransferase (methyltransferase I), a 723-bp fragment was amplified by PCR, which contained the gene odmA encoding the corrinoid protein of O-demethylase. Downstream of odmA, part of the odmB gene encoding methyltransferase I was identified. The amino acid sequence deduced from odmA showed about 60% similarity to the cobalamin-binding domain of methionine synthase from Escherichia coli (MetH) and to corrinoid proteins of methyltransferase systems involved in methanogenesis from methanol and methylamines. The sequence contained the DXHXXG consensus sequence typical for displacement of the dimethylbenzimidazole base of the corrinoid cofactor by a histidine from the protein. Heterologous expression of odmA in E. coli yielded a colourless, oxygen-insensitive apoprotein, which was able to bind one mol cobalamin or methylcobalamin/mol protein. Both of these reconstituted forms of the protein were active in the overall O-demethylation reaction. OdmA reconstituted with hydroxocobalamin and reduced by titanium(III) citrate to the cob(I)alamin form was methylated with vanillate by methyltransferase I in an irreversible reaction. Methylcobalamin carrying OdmA served as methyl group donor for the methylation of tetrahydrofolate by methyltransferase II. This reaction was found to be reversible, since methyltranSferase II also catalysed the methylation of cob(I)alamin containing OdmA with methyltetrahydrofolate.

Acetobacter↗
PubMed2000

Reconstitution of dimethylamine:coenzyme M methyl transfer with a discrete corrinoid protein and two methyltransferases purified from Methanosarcina barkeri.

Methyl transfer from dimethylamine to coenzyme M was reconstituted in vitro for the first time using only highly purified proteins. These proteins isolated from Methanosarcina barkeri included the previously unidentified corrinoid protein MtbC, which copurified with MtbA, the methylcorrinoid:Coenzyme M methyltransferase specific for methanogenesis from methylamines. MtbC binds 1.0 mol of corrinoid cofactor/mol of 24-kDa polypeptide and stimulated dimethylamine:coenzyme M methyl transfer 3.4-fold in a cell extract. Purified MtbC and MtbA were used to assay and purify a dimethylamine:corrinoid methyltransferase, MtbB1. MtbB1 is a 230-kDa protein composed of 51-kDa subunits that do not possess a corrinoid prosthetic group. Purified MtbB1, MtbC, and MtbA were the sole protein requirements for in vitro dimethylamine:coenzyme M methyl transfer. An MtbB1:MtbC ratio of 1 was optimal for coenzyme M methylation with dimethylamine. MtbB1 methylated either corrinoid bound to MtbC or free cob(I)alamin with dimethylamine, indicating MtbB1 carries an active site for dimethylamine demethylation and corrinoid methylation. Experiments in which different proteins of the resolved monomethylamine:coenzyme M methyl transfer reaction replaced proteins involved in dimethylamine:coenzyme M methyl transfer indicated high specificity of MtbB1 and MtbC in dimethylamine:coenzyme M methyl transfer activity. These results indicate MtbB1 demethylates dimethylamine and specifically methylates the corrinoid prosthetic group of MtbC, which is subsequently demethylated by MtbA to methylate coenzyme M during methanogenesis from dimethylamine.

Dimethylamines↗
PubMed1990

High-performance liquid chromatographic separation and dual competitive binding assay of corrinoids in biological material.

Corrinoids were extracted with hot ethanol from human plasma and faeces and separated by high-performance liquid chromatography. The corrinoids (cobalamin and cobalamin analogues) were quantified in the eluted fractions by a dual radioisotope assay using as binders intrinsic factor and haptocorrin to detect cobalamin and total corrinoids, respectively. Recoveries ranged from 37.7 +/- 5.1% for hydroxycobalamin to 75.0 +/- 9.1% for cyanocobalamin. In plasma, the main forms of cobalamin were the coenzymes methylcobalamin and 5'-deoxyadenosylcobalamin (32.1 +/- 13.4 and 28.4 +/- 12.3%, respectively, of total corrinoids). The cobalamin analogue fraction of plasma was eluted with a retention time close to that of cobinamide and of deoxyadenosylcobalamin. In the faeces, most of the corrinoids separated were detected better by the haptocorrin assay than by the intrinsic factor assay. One corrinoid peak was eluted with the same retention time as cobinamide. This peak was detected by haptocorrin assay but not by intrinsic factor assay. It could therefore correspond to cobinamide.

Chromatography, High Pressure Liquid↗
PubMed1993

Isolation of two novel corrinoid proteins from acetate-grown Methanosarcina barkeri.

Two corrinoid proteins with molecular sizes of 480 and 29 kDa are stably methylated by [2-14C]acetate-derived intermediates in cell extracts of aceticlastic Methanosarcina barkeri when methylreductase is inhibited by the addition of bromoethanesulfonic acid. Both 14CH3-proteins have been isolated to near homogeneity and found to be abundant soluble proteins. The larger protein possesses two subunits, of 41.4 and 30.4 kDa, in an equimolar ratio, suggesting an alpha 6 beta 6 conformation with six bound methylated corrinoids per 480-kDa molecule. The 29-kDa protein is a monomer in solution and possesses only one methylated corrinoid. All methyl groups on both proteins are photolabile, but the methylated corrinoid bound to the 29-kDa protein undergoes photolysis at a higher rate than that bound to the 480-kDa protein. The two proteins possess discrete N termini and do not appear to be forms of the same protein in equilibrium. Neither protein has an Fe4S4 cluster, and both have UV-visible spectra most similar to that of a base-on methylated corrinoid. A previously identified methylated protein, designated the unknown A 14CH3-protein, copurifies with the 480-kDa protein and has the same subunit composition. The methyl groups of both isolated 14CH3-proteins are converted to methane in cell extracts. The methylated proteins that accumulate in extracts in the presence of bromoethanesulfonic acid are demethylated by the addition of coenzyme M. Both isolated proteins are abundant novel corrinoid proteins that can methylate and be methylated by intermediates of the methanogenic pathway.

Acetates↗
PubMed1996

Coenzyme M methylase activity of the 480-kilodalton corrinoid protein from Methanosarcina barkeri.

Activity staining of extracts of Methanosarcina barkeri electrophoresed in polyacrylamide gels revealed an additional methylcobalamin:coenzyme M (methylcobalamin:CoM) methyltransferase present in cells grown on acetate but not in those grown on trimethylamine. This methyltransferase is the 480-kDa corrinoid protein previously identified by its methylation following inhibition of methyl-CoM reductase in otherwise methanogenic cell extracts. The methylcobalamin:CoM methyltransferase activity of the purified 480-kDa protein increased from 0.4 to 3.8 micromol/min/mg after incubation with sodium dodecyl sulfate (SDS). Following SDS-polyacrylamide gel electrophoresis analysis of unheated protein samples, a polypeptide with an apparent molecular mass of 48 kDa which possessed methylcobalamin:CoM methyltransferase activity was detected. This polypeptide migrated with an apparent mass of 41 kDa when the 480-kDa protein was heated before electrophoresis, indicating that the alpha subunit is responsible for the activity. The N-terminal sequence of this subunit was 47% similar to the N termini of the A and M isozymes of methylcobalamin:CoM methyltransferase (methyltransferase II). The endogenous methylated corrinoid bound to the beta subunit of the 480-kDa protein could be demethylated by CoM, but not by homocysteine or dithiothreitol, resulting in a Co(I) corrinoid. The Co(I) corrinoid could be remethylated by methyl iodide, and the protein catalyzed a methyl iodide:CoM transmethylation reaction at a rate of 2.3 micromol/min/mg. Methyl-CoM was stoichiometrically produced from CoM, as demonstrated by high-pressure liquid chromatography with indirect photometric detection. Two thiols, 2-mercaptoethanol and mercapto-2-propanol, were poorer substrates than CoM, while several others tested (including 3-mercaptopropanesulfonate) did not serve as methyl acceptors. These data indicate that the 480-kDa corrinoid protein is composed of a novel isozyme of methyltransferase II which remains firmly bound to a corrinoid cofactor binding subunit during isolation.

Acetates↗
PubMed1980

Extracellular metal-free corrinoids from Rhodopseudomonas spheroides.

Rhodopseudomonas spheroides when grown on a medium deficient of cobalt excretes significant amounts of descobaltocorrinoids into the culture broth. If grown in the presence of 4 microM CoCl2 only intracellular cobalt-containing corrinoids are detected. The extracellular corrinoids have been identified as hydrogenobyrinic acid c-amide and hydrogenobyrinic acid a,c-diamide which are accompanied by varying amounts of the corresponding 13-epicorrinoids. The latter, which could not be separated in the metal-free form, are artifacts arising from the excreted descobaltocorrinoids under the alkaline conditions of the culture broth. The red metal-free corrinoids have been converted into the corresponding cobalt-containing corrinoids and were characterized by their CD, UV, 1H NMR, and 13C NMR spectra. Insertion of cobalt into the fraction of hydrogenobyrinic acid c-amide has yielded small amounts of a cobalt-containing corrinoid, for which the structure of 18,19-didehydrocobyrinic acid c-amide is suggested. A 14C-labeled specimen of hydrogenobyrinic acid a,c-diamide was obtained by feeding [14C]acetate to growing cultures of R. spheroides. Experiments with broken cell systems of Propionibacterium shermanii and R. spheroides have indicated that metal-free corrinoids are not precursors of the cobamides. The results are discussed with respect to the final steps of the biosynthesis of vitamin B12.

Chemical Phenomena↗
PubMed2002

A non-dechlorinating strain of Dehalospirillum multivorans: evidence for a key role of the corrinoid cofactor in the synthesis of an active tetrachloroethene dehalogenase.

A strain of Dehalosprillum multivorans, designated strain N, was isolated from the same source as the formerly described tetrachloroethene (PCE)-dechlorinating D. multivorans, herein after referred to as strain K. Neither growing cells nor cell extracts of strain N were able to dechlorinate PCE. The pceA and pceB genes encoding for the PCE-reductive dehalogenase were detected in cells of strain N; and they were 100% homologous to the corresponding genes of strain K. Since the PCE dehalogenase of D. multivorans strain K contains a corrinoid cofactor, the corrinoids of strain N cells were extracted. Analysis of the corrinoids revealed the absence of the specific corrinoid, which is the cofactor of the PCE dehalogenase of strain K cells. RT-PCR of mRNA indicated that the pceA gene was transcribed in strain N cells to a far lower extent than the pceA gene of strain K under the same experimental conditions. Western blot analysis of crude extracts of strain N showed that, if at all, an insignificant amount of the apoprotein of the PCE dehalogenase was present. The results indicate that the inability of strain N to dechlorinate is due to the absence of the corrinoid cofactor of the enzyme mediating PCE dechlorination.

Chromatography, High Pressure Liquid↗
PubMed1991

Separation and study of corrinoid cobalt-ligand isomers by high-performance liquid chromatography.

Vitamin B12 belongs to a group of complex organo-cobalt compounds, the corrinoids. "Complete" corrinoids, such as B12, contain a nucleotide as the cobalt alpha-(lower)ligand. This nucleotide is also connected to the periphery of the corrin ring. The "incomplete" corrinoids, in contrast, contain simple cobalt alpha-ligands, such as water or cyanide. Using analytical reversed-phase and anion-exchange high-performance liquid chromatography (HPLC), we have been able to study the behavior of several aquocyano-"incomplete" corrinoids: three isomeric cobinic acid pentaamides, cobinamide, and cobyric acid, all of which exist as thermally unstable isomers, which separate during HPLC. All but one of these corrinoids gave isomer mixtures of 1:1, the exception giving mixtures of 2:1 to 3:1. The separated stereoisomers had different retention times and were collected from analytical columns for further study.

Chromatography, High Pressure Liquid↗
PubMed1988

Diversity of corrinoids in acetogenic bacteria. P-cresolylcobamide from Sporomusa ovata, 5-methoxy-6-methylbenzimidazolylcobamide from Clostridium formicoaceticum and vitamin B12 from Acetobacterium woodii.

The Co beta-cyanocobamides obtained by cyanide extractions from several acetogenic bacteria were structurally characterized by ultraviolet/visible spectra, proton-nuclear-magnetic-resonance spectra and fast-atom-bombardment mass spectra. p-Cresolycobamide was detected as a major corrinoid from Sporomusa ovata. This 'complete' corrinoid was isolated from an organism for the first time. Instead of the common Co alpha bases of the known and biologically active cobamides, p-cresolylcobamide contained a glycosidically bound cresolyl function that was unable to coordinate to the cobalt of the corrin ring. An additional, previously unknown corrinoid from natural sources, Co alpha-[alpha-(5-methoxy-6-methylbenzimidazolyl)]-Co beta-cyanocobamide, was isolated along with vitamin B12 from Clostridium formicoaceticum. Both homoacetogenic eubacteria were grown on methanol and contained high amounts of corrinoids (greater than 950 nmol/g cell dry mass). Less corrinoid was isolated from Acetobacterium woodii and characterized as vitamin B12.

Bacteria, Anaerobic↗
PubMed1988

5'-Methylbenzimidazolyl-cobamides are the corrinoids from some sulfate-reducing and sulfur-metabolizing bacteria.

The sulfate-reducing bacteria Desulfobacterium autotrophicum, Desulfobulbus propionicus and Archaeoglobus fulgidus (VC-16) and the sulfur-metabolizing archaebacteria Desulfurolobus ambivalens and Thermoplasma acidophilum were found to contain considerable amounts of corrinoids, that were isolated and crystallized in their Co beta-cyano form. In three other sulfur-metabolizing archaebacteria, Thermoproteus neutrophilus, Pyrodictium occultum and Staphylothermus marinus significant amounts of corrinoids were not detected under the isolation methods used. The samples from the three sulfate-reducers were identified with Co alpha-[alpha-(5'-methylbenzimidazolyl)]-Co beta-cyanocobamide. This corrinoid was also obtained from a 5-methylbenzimidazole-supplemented Propionibacterium fermentation and was structurally characterized by ultraviolet/visible, CD, fast-atom-bombardment MS, 1H-and 13C-NMR spectroscopy. Also the major corrinoid from T. acidophilum was (tentatively) analyzed as a 5'-methylbenzimidazolyl-cobamide, whereas the main corrinoid from D. ambivalens was indicated to be vitamin B12 (a 5',6'-dimethylbenzimidazolyl-cobamide). The 5'-methylbenzimidazolylcobamides are found here as the common corrins of some sulfate-reducing and sulfur-metabolizing bacteria. The structural diversity due to the differing nucleotide bases of the corrins examined here and in methanogenic and acetogenic bacteria appears not to correlate to the biological function(s) of the corrins, but rather to be determined by biosynthetic properties of these organisms under natural growth conditions.

Bacteria↗