Methanogens biosynthesis

The enzyme is present in large amounts in acetogenic bacteria, where it is involved in an unusual pathway for fixation of C02 with the formation of acetate (25,26). In acetogens this reaction is involved both in production of energy, with acetate as a waste product, and in biosynthesis of cell constituents starting from acetate. CO oxidoreductase is also present in methanogenic bacteria, where it is used in biosynthetic metabolism (25, 27). 

DiMarco, A. A., T. A. Bobik, and R. S. Wolfe, Unusual coenzymes of methanogenesis. Ann. Rev. Biochem. 59 355 (1990). A review of the recently characterized coenzymes required for the biosynthesis of methane in methanogenic bacteria. 

Many methanogenic archaeabacteria lack cysteinyl-tRNA synthetase (CysRS). Interestingly, a Class II enzyme called O-phosphoseryl-tRNA synthetase (SepRS) acylates tRNA with O-phosphoserine (Sep) to form Sep-tRNA , which is then converted to Cys-tRNA by the enzyme Sep-tRNA Cys-tRNA synthase (SepCysS). It has been proposed that this indirect pathway may be the sole route for cysteine biosynthesis in these organisms (9). The crystal structure of SepRS was recently... 

Almost all methanogen species can grow on H2+CO2 carrying out autotrophic cell carbon biosynthesis [183]. Due to simplicity of the catabolites, C02-reduction to methane has been extensively used as a model system to study the biochemistry of methanogenesis. Most of this work has used M. thermoautotrophicum, and to a lesser extent, M. barkeri. 

In regard to the pathways for biosynthesis of individual archaeol phospholipids in methanogens, a study on the incorporation and turnover of P in archaeol and... 

Fig. 13. Proposed mechanism for biosynthesis of caldarchaeol phosphoglycolipids in methanogens,...

The observation that the fatty acid synthetase (FAS) in H. cutirubrum is strongly inhibited by high salt concentration while the mevalonate enzyme system for isoprenoid biosynthesis has an absolute requirement for high salt concentration (see section 4.1) may offer a clue to the mechanism of evolution of extreme halophiles from non-halophilic, or moderately halophilic precursors, and possibly also for the evolution of the methanogens and extreme thermophiles. The following hypothetical scenarios are offered for discussion (see ref [107] and Figs. 9, 14) ... 

Koga Y., Nishihara M., Morii H., and Akagawa-MatsushitaM. (1993) Ether polar lipids of methanogenic bacteria structures, comparative aspects, and biosynthesis. Microbiol. Rev. 57, 164-182. 

Small Precursor Molecules Such as Acetate Can Be Sufficient for Retroanalysis -Biosynthesis of Heterocyclic Coenzymes in Methanogenic Bacteria... 

Mercury. In the biosynthesis of methylmercury by extracts from a methanogenic bacterium, electrophilic attack on the Co—C bond of methylcobalamin results in methyl transfer from Co " " of methylcobalamin (CH3B12) to Hg " " with the synthesis of methyl- and dimethylmercury ... 

While recent progress has been impressive, there are still many unsolved problems and challenges in cofactor metabolism some examples are as follows The mechanistic enzymology of cofactor biosynthesis in the methanogens is still in its infancy, cofactor catabolism is poorly understood, and cofactors have not... 

This review on the biosynthesis of methanogenic coenzymes in the methanoarchaea will constitute an update of ... 

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