抄録
It has been known that the three propionamide groups at the positions b, d and e of the corrin ring of cobalamin are easily hydrolyzed and give the mixture of cobalamin carboxylic acids, B_<12>-(COOH)_<1〜3>, possessing 1 to 3 propionic aicd group(s) in place of propionamide group(s). The present paper deals with the in vivo and in vitro formation of the coenzyme form, i.e. 5'-deoxyadenosyl derivative, from each of cobalamin carboxylic acids by Propionibacterium shermanii. When cyanocobalamin mono-, di- or tricarboxylic acid was added to the growing culture of Pr. shermanii, all of these compounds were found to convert to the coenzyme forms almost quantitatively. During the cultivation period, 50 to 70% of the carboxylic groups was amidated. In the case of the incubation of aquocobalamin or its carboxylic acid analogs with the crude extract of the same bacteria, the comparative rates of conversions to the coenzyme forms were as follows : OH-B_<12> 77,OH-B_<12>-(COOH)_1 54,OH-B_<12>-(COOH)_2 32,OH-B_<12>-(COOH)_3 7. With respect to the deoxyadenosylation of the three isomers of aquocobalamin monocarboxylic acid, the conversion rate of b-isomer to the coenzyme form was substantially the same as that of aquocobalamin but d- and e-isomers could hardly serve as the substrates.
