[Participation of 5'-deoxyadenosyl-B12 in regulating methylation of tRNA]

The effects of different forms of cobalamines on the activities of tRNA-methylases of Zajdela ascite hepatoma were studied. Of six cobamides studied 5'-deoxyadenosyl-B12 and factor B containing as a ligand HSO3 in the concentrations of 2.4-10(-5) and 4.8-10(-5) M inhibited the tRNA-methylase activity by 21% and 15% correspondingly. The inhibitory effect of 5'-deoxyadenosyl-B12 is probably dependent on the adenosyl part of the molecule. 5'deoxyadenosyl-B12 exerted a selective effect of Zajdela ascite hepatoma tRNA-methylases, inhibiting largely the activity of 5-methyl cytosine methylase during the methylation of the E. coli K12W6 tRNA and yeast tRNA1 Val.