The Catalysis of the Auto-Oxidation of 2-Mercaptoethanol and Other Thiols by Vitamin B12 Derivatives. Polarographic and Other Investigations

Jl, Peel

doi:10.1042/bj0880296

Cited by 74 publications

(33 citation statements)

References 21 publications

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“…The isolation of apparently identical organisms from the rumens of animals on two widely different pasture types from separate localities suggests that the small coccus isolated is commonly present in the rumen, while the relatively simple nutritional requirements and broad specificity for carbohydrates indicate its competence in the ruminal environment. The organism was found to be a strict anaerobe, and it is possible that the effect of vitamin B12 observed by Dick et al (1963) was related to the achievement of anaerobiosis by the Peel effect (Peel 1963). Factor B was shown to be 4000 times as effective as vitamin B12 in catalysing the oxidation of thiols by molecular oxygen (Peel 1963), but in the present experiments neither vitamin B12 nor factor B had any effect on the rate of degradation of heliotrine.…”

Section: (G) Reduction Of Heliotrine With Molecular Hydrogencontrasting

confidence: 40%

“…The organism was found to be a strict anaerobe, and it is possible that the effect of vitamin B12 observed by Dick et al (1963) was related to the achievement of anaerobiosis by the Peel effect (Peel 1963). Factor B was shown to be 4000 times as effective as vitamin B12 in catalysing the oxidation of thiols by molecular oxygen (Peel 1963), but in the present experiments neither vitamin B12 nor factor B had any effect on the rate of degradation of heliotrine. There was no demonstrable requirement of the isolated organism for vitamin B12 in the culture medium and negligible quantities of B 12 -active substances were present after heliotrine was degraded.…”

Section: (G) Reduction Of Heliotrine With Molecular Hydrogencontrasting

confidence: 40%

“…Factor B has been found to give an enhanced Peel effect (Peel 1963), and so was compared with vitamin B 12 • Replicate flasks were set up, each containing 100 ml of lightly centrifuged rumen liquor, adjusted to pH 6·9 under 00 2 , and O· 5 mg/ml of added heliotrine. One flask was untreated, one contained 2·0 fLg/ml vitamin B 12 , and the third an equivalent amount of factor B (1'3 fLg/ml).…”

Section: (D) Growth and Degradation Of Heliotrine In The Pre8ence Andmentioning

confidence: 99%

“…The stoichiometry of this reaction has been examined and it has been shown that the substrates are not incorporated into bacterial substance, but the reaction appears to serve as an energy source. It is suggested that the stimulation in rate by vitamin B12 observed by Dick et al (1963) may have been due to its known capacity to catalyse the oxidation of thiols by molecular oxygen and thus to remove traces of oxygen from solution (Peel 1963}. …”

Section: Introductionmentioning

confidence: 99%

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Reduction of Heliotrine by A Rumen Microorganism

Russell¹,

Smith²

1968

Aust. Jnl. Of Bio. Sci.

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SummaryA small Gram-negative coccus, which brings about the reductive fission of the hepatotoxic pyrrolizidine alkaloids, has been isolated from the rumen contents of Australian Merino sheep. The organism was cultured in a partially defined medium, without rumen fluid, but containing yeast extract. Strictly anaerobic conditions and the presence of carbon dioxide were essential for growth. With limiting quantities of yeast extract, growth was greatly stimulated by any of several carbohydrates or moderately stimulated by the alkaloid heliotrine plus hydrogen. The products of the reductive cleavage of heliotrine were heliotric acid and 7()(-hydroxy-l-methylene-8()(-pyrrolizidine. One mole of hydrogen reduced one mole of heliotrine to produce one mole each of the two products, accounting completely for the substrate consumed. Formate in stoichiometric quantities could replace molecular hydrogen as hydrogen donor in the reaction in which heliotrine acted as hydrogen acceptor. With [UCJformate as hydrogen donor 14CO. was evolved in stoichiometric amounts. The additional growth brought about by the degradation of heliotrine was proportional to the amount of heliotrine degraded, the organism appearing to derive energy from the reaction. Under strictly anaerobic conditions neither growth of the organism nor degradation of heliotrine was dependent on or stimulated by the presence of vitamin B12 in the medium. A method is described for the estimation of heliotrine.

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Section: (G) Reduction Of Heliotrine With Molecular Hydrogencontrasting

confidence: 40%

Section: (G) Reduction Of Heliotrine With Molecular Hydrogencontrasting

confidence: 40%

Section: (D) Growth and Degradation Of Heliotrine In The Pre8ence Andmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Reduction of Heliotrine by A Rumen Microorganism

Russell¹,

Smith²

1968

Aust. Jnl. Of Bio. Sci.

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“…with a vortex mixer. This relative insensitivity to oxygen makes it unlikely that the stimulating effect of cyanocobalamin was due to scavenging of residual oxygen by the catalytic effect of vitamin B1, on thiol oxidation (Peel, 1963).…”

Section: Resultsmentioning

confidence: 99%

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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Cob(I)alamin als Katalysator. 6. Mitteilung [1]. Bildung und Fragmentierung von Alkylcobalaminen, ein Gleichgewichtsprozess zwischen nukleophiler Addition und reduktiver Fragmentierung

Fischli

Müller

1980

Helvetica Chimica Acta

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Cob(1)alamin as Catalyst. 6.Communication [l]. Formation and Fragmentation of Alkylcobalamins: the Nucleophilic Addition -Reductive Fragmentation Equilibrium SummaryIsolated olefines can be saturated using catalytic amounts of cob(1)alamin in aqueous acetic acid; as electron source an excess of zinc dust is added to the solution containing the homogeneous catalyst. During this overall hydrogenation of isolated double bonds intermediate alkylcobalamins are formed (compare e.g. Schemes 2, 4, 5, 7 and 12). Clear evidence is presented that the nucleophilic attack on the isolated double bond is carried out by cob(1)alamin and not by cob(I1)alamin also present in the system (see Scheme 3b and 3c). As this catalytic saturation of olefins depends on the pH of the solution, characterized by a slow reaction at pH = 7.0 compared to the same reduction in aqueous acetic acid (see Scheme 2, 2+4, and Scheme 3a), it is reasonable to accept the participation of an electrophilic attack by a proton during the generation of alkylcobalamins. -We use the term nucleophilic addition to describe the formation of alkylcobalamins from a proton, an olefin and cob (1)alamin (compare Schemes 4-7 and 12).A special sequence of experiments showed the nucleophilic addition to be regioselective. Preferentially the higher substituted alkylcobalamin revealed to be produced. Therefore, the nucleophilic addition of cob (1)alamin follows the Murkownikoff rule (compare chap. 4: formation and fragmentation of P-hydroxyalkylcobalamins).Under the reaction conditions applied the intermediate alkylcobalamins can be present in base-on and base-off forms. They are known to exist as octahedral complexes and might also be stable to some extent as tetragonal-pyramidal species. In addition the base-off forms can partially be protonated at the dimethylbenzimidazole moiety in aqueous acetic acid (compare Scheme 12). From this equilibrium of intermediate alkylcobalamins three modes of decay disclosed to be possible: (i)The reductive fragmentation leading to an olefin, a proton, and cob (1)alamin is the formal retro-reaction of the nucleophilic addition (see Schemes 2, 4 and 6-12). This equilibrium of an associated alkylcobalamin and the corresponding dissociation products revealed to be a fast process compared to the re-ductive cleavage of the Co, C-bond cited below (s. (iii)). (ii) As the second reaction pattern an oxidative fragmentation producing an olefin, a hydroxy anion (or water, respectively) and cob(II1)alamin has been observed (see Schemes 7, 8, 10 and 12). (iii) The slow reductive cleavage of the Co, C-bond, initiated by addition of electrons (see [la] [24]), was the third reaction path observed (see Schemes 2, 4-8 and 10-12). -The stereochemistry of the three transformations originating from the intermediate alkylcobalamins is unknown up to now. The antiperiplanar pattern of the fragmentation reactions presented in the Schemes has been chosen arbitrarily (see e.g. Scheme 12). 1. Einleitung. -Alkylcobalamine, gut bekannte organometallische Verbindungen, d...

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The Catalysis of the Auto-Oxidation of 2-Mercaptoethanol and Other Thiols by Vitamin B12 Derivatives. Polarographic and Other Investigations

Cited by 74 publications

References 21 publications

Reduction of Heliotrine by A Rumen Microorganism

Reduction of Heliotrine by A Rumen Microorganism

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

Cob(I)alamin als Katalysator. 6. Mitteilung [1]. Bildung und Fragmentierung von Alkylcobalaminen, ein Gleichgewichtsprozess zwischen nukleophiler Addition und reduktiver Fragmentierung

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