title: Constitutive behavior of methionyl-tRNA synthetase compared to repressible behavior of methionine adenosyltransferase in mammalian cells.
abstract: Methionine adenosyltransferase, one of the two major enzymes utilizing methionine, is regulated by the levels of methionine in the growth medium (Jacobsen, S.J., Hoffman, R.M. and Erbe, R.W. (1980) J. Natl. Cancer Inst. 65, 1237--1244, and Caboche, M. and Mulsant, P. (1978) Somatic Cell Genet. 4, 407--421). We report here that methionyl-tRNA synthetase, unlike methionine adenosyltransferase, behaves in a constitutive manner with respect to the concentration of methionine in the culture medium. This behavior is seen in Chinese hamster ovary cells and in normal diploid and SV40-transformed human fibroblasts. Although the kinetics of regulation of methionine adenosyltransferase and methionyl-tRNA synthetase by exogenous methionine are clearly different, the levels of the two enzymes in the human cell lines are similar.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D004794:Enzyme Repression / Q000187:drug effects; D005260:Female; D005347:Fibroblasts; D006801:Humans; D008647:Mesocricetus; D008715:Methionine / Q000378:metabolism* / Q000494:pharmacology; D008716:Methionine Adenosyltransferase / Q000378:metabolism*; D008718:Methionine-tRNA Ligase / Q000378:metabolism*; D010053:Ovary; D014166:Transferases / Q000378:metabolism*
chemical_list: D008715:Methionine; D014166:Transferases; D008716:Methionine Adenosyltransferase; D000604:Amino Acyl-tRNA Synthetases; D008718:Methionine-tRNA Ligase