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Appl Environ Microbiol. 1977 March; 33(3): 515-521
Copyright © 1977 American Society for Microbiology. All Rights Reserved.

Form of Vitamin B₁₂ and Its Role in a Methanol-Utilizing Bacterium Protaminobacter ruber

Department of Food Science and Technology, Nagoya University, Furo-Cho, Chikusa-Ku, Nagoya 464, Japan

ABSTRACT

A methanol-utilizing bacterium, Protaminobacter ruber, produced a large amount of vitamin B₁₂. The compounds were isolated from the cells and identified as methylcobalamin (methyl-B₁₂) and adenosylcobalamin (adenosyl-B₁₂) by various tests. The variation in the form of B₁₂ during cultivation was examined by bioautography with cellulose acetate membrane electrophoresis. Methyl-B₁₂ and adenosyl-B₁₂ were the two main B₁₂ compounds produced in the various phases of bacterial growth. The ratio of the amount of methyl-B₁₂ to total B₁₂ compounds was higher during the earlier phases of growth. After the logarithmic phase, adenosyl-B₁₂ was the predominant form. The existence of N⁵-methyltetrahydrofolate:homocysteine transmethylase and methyl-B₁₂:homocysteine transmethylase was demonstrated in cell-free extracts of Protaminobacter ruber. Methyl-B₁₂ in P. ruber seems to function mainly in the B₁₂-dependent methionine synthetase system.