Recent advances in elucidation of biological corrinoid functions

Abstract

Eleven adenosylcorrinoid-dependent rearrangements and elimination reactions have been described during the last four decades of vitamin B12 research. In contrast, only the cobamide-dependent methionine synthase was well established as a corrinoid-dependent methyl transfer reaction. yet, investigations during the last few years revealed nine additional corrinoid-dependent methyltransferases. Many of these reactions are catalyzed by bacteria which possess a distinct C1 metabolism. Notably acetogenic and methanogenic bacteria carry out such methyl transfers in their anabolism and catabolism. Tetrahydrofolate or a similar pterine derivative is a key intermediate in these reactions. It functions as methyl acceptor and the methylated tetrahydrofolate serves as a methyl donor.

Microbial Methylation of Metalloids: Arsenic, Antimony, and Bismuth

“…It is clear that the transfer of methyl groups from methylcobalamin to arsenic over and above that of nonenzymatic controls was demonstrated (175). Methylcobalamin has been increasingly implicated in a range of methylation reactions in addition to its well-known role in methionine biosynthesis (94,143,226).…”

Shedding light on anaerobic benzene ring degradation: a process unique to prokaryotes?

“…Other modifications including removal of hydroxyl, methoxyl, amino, and acyl groups are also being studied (24,55,57) (Fig. 1).…”

Effects of Plant Residue Extract and Cobalamin on Growth and Propionate Production of Propionicimonas paludicola Isolated from Plant Residue in Irrigated Rice Field Soil

“…The methanogenic strain excreted 80% of the B 12 compound produced into the medium without cell lysis 21) . The involvement of corrinoids in anaerobic dehalogenation has also been reported 19,26,29) . Thus, it is likely that the cobalamin compound produced endogenously by these microbial groups serves as an exogenous source of cobalamin for other microbial groups in the community.…”

“…Two major groups in anaerobic microbial ecosystems, acetogens and methanogens, possess distinct metabolisms relating to the cobalamin compound. Acetyl-coenzyme A biosynthesis in acetogenic bacteria as well as the acetate catabolism of methanogens involves sim- ilar corrinoid-dependent methyltransferases 29) . It has been reported that various acetogenic anaerobic bacteria including Acetobacterium spp.…”