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A member of the vitamin B12 group has been identified as the red chromophore of reddish brown enzyme fractions obtained from Clostridium sticklandii. An orange compound which appears to be identical with the coenzyme form of pseudovitamin B12 (or adenine-B12 coenzyme) discovered by Barker et al. (Proe. Natl. Acad. Sci. U. S., 44, 1093, 1958) is obtained if preparations are protected from visible light during the isolation procedure. The concentration of adenine-B12 coenzyme in C. sticklandii is about twice that in Clostridium tetanomorphum and at least one-third that of the total B12 coenzyme in Propionibacterium shermanii (Barker, personal communication). The latter organism is one of the richest known sources of B12 coenzvmes which function in the isomerization of suceinyl coenzvme A to methyl malonyl coenzyme A (E. R. Stadtman et al., Biochem. Biophys. Research Commun., 2 .1, 1960). In C. tetanomorphum, the B12 coenzymes catalyze the isomerization of glutamate to methyl aspartate (Barker et al., Proe. Natl. Acad. Sci. U. S., 44, 1093, 1958). Since the metabolism of C. sticklandii is concerned mainly with the catalysis of a Stickland type fermentation and in the transformation of one-carbon compounds (Stadtman and White, J. Bacteriol., 67, 651, 1954), the presence in this organism of abnormally high concentrations of B12 coenzyme suggested a possible role of this coenzyme in one of these exaggerated metabolic processes. Indirect evidence against its involvement in the Stickland fermentation is derived from the fact that two other amino acid fermenting bacteria, Clostridium sporogenes and Clostridium lentoputrescens, fail to produce significant quantities of the B12 coenzvmes when grown in a medium identical with that used for C. sticklandii (table 1). On the other hand, a functional role in the metabolism of one-carbon compounds is suggested by the discovery that the amount of B12 coenzyme accumulating in C. sticklandii is influenced markedly by the level of its one-carbon metabolism. Thus, when grown in a chemically defined medium (Stadtman, J. Bacteriol., 67, 314, 1954) containing either (1) 0.2 per cent each

SYNTHESIS OF ADENINE-B 12 COENZYME BY CLOSTRIDIUM STICKLANDII: RELATIONSHIP TO ONE-CARBON METABOLISM

SYNTHESIS OF ADENINE-B ₁₂ COENZYME BY CLOSTRIDIUM STICKLANDII: RELATIONSHIP TO ONE-CARBON METABOLISM