Level of methionine synthase activity and interconversion of methylcobalamin and adenosylcobalamin in a facultative methylotroph, Protaminobacter ruber

J Nutr Sci Vitaminol (Tokyo). 1980;26(6):557-69. doi: 10.3177/jnsv.26.557.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / analysis*
  • Cobamides / metabolism*
  • Methyltransferases / analysis*
  • Pseudomonadaceae / enzymology
  • Pseudomonadaceae / growth & development
  • Pseudomonadaceae / metabolism*
  • Time Factors
  • Vitamin B 12 / analogs & derivatives*
  • Vitamin B 12 / metabolism
  • Vitamin B 12 / pharmacology


  • Cobamides
  • mecobalamin
  • Methyltransferases
  • 5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase
  • cobamamide
  • Vitamin B 12