[Methylcobalamin-dependent methylation of proteins during malignant degeneration]

A capacity of methylcobalamine (14CH3-B12) to methylate proteins from rat liver tissue and from Zajdela ascites hepatoma was studied. The rate of methylation using 14CH3B12 was compared with that of the universal donor of methyl groups--S-adenosyl-L-(methyl-14C[methionine], Ado-met)-14CH3-B12 methylated proteins from Zajdela ascites hepatoma 6-9-fold and proteins from liver tissue 50-60-fold more intensively as compared with Ado-met in vitro. The methylating ability of 14CH3-B12 depended on protein concentration. Liver proteins were methylated at the rate 2-2.5-fold higher than Zajdela ascites hepatoma proteins. At the same time, Ado-met was the most effective donor of 14CH3 groups for proteins of Zajdela ascites hepatoma. Heat treatment of proteins increased the rate of their methylation using 14CH2-B12 by 10-20%; when Ado-met was used the transfer of CH3 groups was decreased 2-5-fold.