title: Studies on the mechanism of inhibition of tRNA methylation by 3,4-dihydroxyphenylethylamine.
abstract: A Lineweaver-Burk analysis of a kinetic study of tRNA methylation by a 30-50% (NH4)2SO4 fraction from a weanling rat liver extract showed competitive inhibition with a Km for S-adenosylmethionine = 0.66 - 10(-6) M and a Ki for 3,4-dihydroxyphenylethylamine (dopamine) = 4 - 10(-5) M. The dopamine-inhibited methylation of tRNA appears to be linear with time. Rapid-flow dialysis studies indicated a S-adenosylmethionine binding constant of 0.65 - 10(-6) M. Dopamine appeared to interfere with the binding of S-adenosylmethionine to the weanling rat liver protein preparation but did not affect the binding of S-adenosylmethionine to protein in several systems in which dopamine did not inhibit tRNA methylase activity.
mesh_terms: D000818:Animals; D004298:Dopamine / Q000494:pharmacology*; D005260:Female; D006657:Histones / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D011496:Protein Methyltransferases / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D051381:Rats; D012436:S-Adenosylmethionine / Q000494:pharmacology; D013095:Spermidine / Q000494:pharmacology; D012359:tRNA Methyltransferases / Q000378:metabolism*
chemical_list: D006657:Histones; D012436:S-Adenosylmethionine; D012343:RNA, Transfer; D011496:Protein Methyltransferases; D012359:tRNA Methyltransferases; D013095:Spermidine; D004298:Dopamine