Role of vitamin B12 and enzymes related to methylmalonyl-CoA mutase in a methanol-utilizing bacterium, Protaminobacter ruber.

A methanol-utilizing bacterium, Protaminobacter ruber, required cobalt ion or vitamin B12 as its growth factor, which could be replaced by succinate among various additions to the cobalt-deficient medium. The presence of adenosylcobalamin (adenosyl-B12)-dependent methylmalonyl-coenzyme A (CoA) mutase was demonstrated in the cell-free extracts of P. ruber. The specific activity of this mutase was not only fairly high in comparison with that reported with other organisms but also detected at a similar level throughout the cultivation period. The cell-free extracts of P. ruber grown on non-C1 compounds as a sole carbon and energy source also had methylmalonyl-CoA mutase activity. Furthermore, the extracts of this microorganism catalyzed the reactions from propionyl-CoA to succinyl-CoA and from alpha-ketoglutarate to alpha-hydroxyglutarate.