title: Level of methionine synthase activity and interconversion of methylcobalamin and adenosylcobalamin in a facultative methylotroph, Protaminobacter ruber.
abstract: Protaminobacter ruber was cultured in a medium containing [57Co]cyanocobalamin with a "two-step cultivation method" and the forms of vitamin B12 compounds in the cells were examined. Methylcobalamin was detected in the early phases of growth and reached a maximum of about 40% of all cobalamins extracted from the cells. In the stationary phase of growth, almost all cobalamins consisted of adenosylcobalamin. Recultivation of the cells of the stationary phase in a fresh medium resulted in the conversion of adenosylcobalamin into methylcobalamin. Interconversion of methylcobalamin and adenosylcobalamin was presumed from these facts. The formation of adenosylcobalamin from methylcobalamin was demonstrated with a cell-free extract system from P. ruber. The rate of conversion of methylcobalamin into adenosylcobalamin was highest among several cobalamin analogs tested. Propylation of 5-methyltetrahydrofolate: homocysteine methyltransferase with 1-iodopropane did not affect this conversion reaction, which was probably catalyzed by methyltransferase and adenosyltransferase.
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000032:analysis*; D003038:Cobamides / Q000378:metabolism*; D008780:Methyltransferases / Q000032:analysis*; D011548:Pseudomonadaceae / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D013997:Time Factors; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology
chemical_list: D003038:Cobamides; C019476:mecobalamin; D008780:Methyltransferases; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; C000913:cobamamide; D014805:Vitamin B 12