Transfer RNA methyltransferase and glycine N-methyltransferase activity during Rana pipiens development.

Changes in the activity of the tRNA methyltransferases have been found in all differentiating systems studied. Activity was examined in extracts of Rana pipiens embryos and in larval and adult liver by in vitro assay using S-adenosyl-L-[methyl-‘4C]methionine as the methyl donor. Specific activities of tRNA methyltransferases decreased, beginning with the time of feeding, when using high concentrations of the crude liver enzyme. A new methyltransferase activity, glycine Nmethyltransferase, appeared at the time of feeding. Apparently, the glycine methyltransferase is active before the onset of any of the characteristic metamorphic changes of other liver enzymes. Using partially purified enzyme from adult liver, the K, of glycine methyltransferase for Sadenosylmethionine is 0.3 mM and the K, for S-adenosylhomocysteine, a competitive inhibitor, is 0.08 mM.