Biosynthesis of methane from the methyl moiety of methylcobalamin

Blaylock, Barbara A.; Stadtman, Thressa C.

doi:10.1016/0006-291x(63)90023-8

Cited by 56 publications

(10 citation statements)

References 9 publications

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“…It required catalytic amounts of corrins. Qther workers have shown that methylcobalamin (MeCbl) is a substrate for methanogenesis in extracts of M. bryantii and Methanosarcina barkeri (3,4,30). In our studies, corrins stimulated the demethylation of CH3-S-CoM.…”

supporting

confidence: 53%

Inhibition by corrins of the ATP-dependent activation and CO2 reduction by the methylreductase system in Methanobacterium bryantii

Whitman¹,

Wolfe²

1987

J Bacteriol

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Corrins inhibited the ATP-dependent activation of the methylreductase system and the methyl coenzyme M-dependent reduction of CO2 in extracts of Methanobacterium bryantii resolved from low-molecular-weight factors. The concentrations of cobinamides and cobamides required for one-half of maximal inhibition of the ATP-depen4ent activation were between 1 and 5 ,M. Cobinamides were more inhibitory at lower concentratiops than cobamides. Deoxyadenosylcobalamin was not inhibitory at concentrations up to 25 ,uM. The inhibition of CO2 reduction was competitive with respect to CO2. The concentration of methylcobalamin required for one-half of maximal inhibition was 5 ,M. Other cobamideg inhibited at similar concentrations, but diaquacobinami4e inhibited at lower concentrations. With respect to their affinities and specificities for corrins, inhibition of both the ATP-dependent activation'and CO2 reduction closely resembled the corrindependent activation of the methylreductase described in similar extracts (W. B. Whitman and R. S. Wolfe, J. Bacteriol. 164:165-172, 1985). However, whether the multiple effects of corrins are due to action at a single site is unknown.The effect of corrins (cobamides and cobinamides) on in vitro methanogenesis is enigmatic. On one hand, small amounts of corrins stimulate the methyl coenzyme M (CH3-S-CoM) methylreductase system three-to fivefold (29). On the other hand, as reportfd in this communication, corrins also inhibit CO2 reduction as well as ATP activation of the methylreductase system. This system (23) catalyzes the reduction of CH3-S-CoM to form methane:Mg2+, ATP, B, FAD Most of our information about the methylreductase system comes from studies of Methanobacterium thermoautotrophicum. In M. thermoautotrophicum, the enzyme system contains at least four proteins (11,17). Component C, which contains the nickel tetrapyrrole factor F-430 and tightly bound CoM, and the colorless A2 protein, which binds to N6-ATP agarose, have been purified to homogeneity (6,7,14,22). The methylreductase system also requires a lowmolecular-weight factor of unknown function called compo- In addition to the components of the methylreductase system, this reaction requires two additional coenzymes, methanofuran (MF) and tetrahydromethanopterin (MP) (9,13,15,16,21,24). These coenzymes are additional C-1 carriers at the formyl, methine, methylene, and methyl levels of oxidation (8, 15), and some of the enzymes necessary for their activity have been identified in extracts (5,12). Small amounts of CH3-S-CoM are also necessary to initiate * Corresponding author. CO2 reduction. However, the precise role of CH3-S-CoM is not known (9, 20).We described a corrin-dependent activation of the methylreductase system in extracts of the mesophile Methanobacterium bryantii (29). This activation was unlike previously described effects of corrins in methanogenesis. It required catalytic amounts of corrins. Qther workers have shown that methylcobalamin (MeCbl) is a substrate for methanogenesis in extracts of M. bryantii and Metha...

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supporting

confidence: 53%

Inhibition by corrins of the ATP-dependent activation and CO2 reduction by the methylreductase system in Methanobacterium bryantii

Whitman¹,

Wolfe²

1987

J Bacteriol

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“…The properties of the particulate preparations, though not always as clear-cut as might be expected from soluble enzymes, resemble in certain details those of the extracts of Methanosarcinu barkerii studied by Blaylock & Stadtman (1963; see also Stadtman, 1967): vitamin B1, is involved (it stimulates and becomes bleached during the reaction), and adenine nucleotides stimulate. But the source of the methane is the 3-C group of pyruvate, which it is not in extracts of M .…”

Section: Be-mentioning

confidence: 87%

Methane as a Minor Product of Pyruvate Metabolism by Sulphate-reducing and Other Bacteria

Postgate

1969

Journal of General Microbiology

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SUMMARYDisrupted cells of some Desulfovibrio species, of Desulfotomaculum ruminis and of certain other anaerobes produced methane as a minor product of pyruvic phosphoroclasm. In one Desulfovibrio species the reaction, which was not specially sensitive to air, involved vitamin BI2, coenzyme A, thiamine pyrophosphate, magnesium ions and acetyl phosphate. Adenine and other nucleotides stimulated the reaction; a mixture of ATP and AMP was most effective. Methionine stimulated the reaction but the other methyl donors did not. In optimal conditions methane accounted for 0.1 to 0.02 mole % of the pyruvate metabolized, formed at 20 to 30 nl.CH,/mg. bacterial protein/hr. Tests in D20 indicated that the methane came from the methyl-carbon of pyruvate ; correspondingly, ethane formation from a-ketobutyrate was detected. I N T R O D U C T I O NSisler & ZoBell (I 95 I) reported that certain cultures of marine sulphate-reducing bacteria, pure by normal criteria, formed methane during growth in lactate + sulphate media. Though occasional references to this finding have appeared, and Sorokin (1956) failed to conlirm it, interest has tended to centre on the disputed question of the oxidation of methane (and other hydrocarbons) by desulfovibrios (e.g. Sorokin, 1957 ;Davis & Yarbrough, 1966). Methane formation by phosphoroclastic preparations from strains of sulphate-reducing bacteria was reported briefly by Postgate (I 969). The present paper describes the reaction in one Desulfovibrio strain in more detail and reports its occurrence in other bacteria. METHODSCultivation. Desulfovibrio desulfuricans ;variety azotovorans, strain BERRE s (NCIB 8388) was grown at 30" in a 600 ml. continuous-culture apparatus (Baker, 1968) at dilution rates ranging from 0.05 to 0.1 hr-l. The medium used was deficient in k e d nitrogen ; it contained (g./l.) : KH2P04, 0.5 ; Na,S04 4-5 ; CaCl, . 2H,O, 0.06 ; MgSO, . 7H20, 0.06; FeSO,. 7H20, 0.004; sodium lactate, 6; sodium citrate, 0.3 (to prevent precipitation of metal hydroxides) in distilled water; plus 10 ml. of a trace element mixture containing (mg.) : H8B08, 2'32; CoSO, . 7H20, 95-6; CuSO, . 5H20, 8 ; MnSO, . 4H20, 8 ; NaMoO, .2H,O, 30 ; ZnSO, . 7H20, 174 in I 1. distilled water. The complete medium was at pH 8-2; the atmosphere was N, containing 6 to 8% (v/v) CO,.The CO, buffered the culture to between pH 7.6 and 8, and displaced excess sulphide.

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“…The conversion ofmethylcobala-min into methane by extracts of Metharo8arcina was first observed by Blaylock & Stadtman (1963, after the discovery that this compound can serve as a methyl donor in methionine synthesis: Vol. 105 5 H. A. BARKER They found that either pyruvate or hydrogen gas can serve as a reductant in the enzymic system.…”

Section: Methylcobalamin +Homocysteine Cobalamin + Methioninementioning

confidence: 99%

Biochemical functions of corrinoid compounds. The sixth Hopkins memorial lecture

Barker¹

1967

Biochemical Journal

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Biosynthesis of methane from the methyl moiety of methylcobalamin

Cited by 56 publications

References 9 publications

Inhibition by corrins of the ATP-dependent activation and CO2 reduction by the methylreductase system in Methanobacterium bryantii

Inhibition by corrins of the ATP-dependent activation and CO2 reduction by the methylreductase system in Methanobacterium bryantii

Methane as a Minor Product of Pyruvate Metabolism by Sulphate-reducing and Other Bacteria

Biochemical functions of corrinoid compounds. The sixth Hopkins memorial lecture

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