title: Induction and repression in the S-adenosylmethionine and methionine biosynthetic systems of Saccharomyces cerevisiae.
abstract: Two methionine biosynthetic enzymes and the methionine adenosyltransferase are repressed in Saccharomyces cerevisiae when grown under conditions where the intracellular levels of S-adenosylmethionine are high. The nature of the co-repressor molecule of this repression was investigated by following the intracellular levels of methionine, S-adenosylmethionine, and S-adenosylhomocysteine, as well as enzyme activities, after growth under various conditions. Under all of the conditions found to repress these enzymes, there is an accompanying induction of the S-adenosylmethionine-homocysteine methyltransferase which suggests that this enzyme may play a key role in the regulation of S-adenosylmethionine and methionine balance and synthesis. S-methylmethionine also induces the methyltransferase, but unlike S-adenosylmethionine, it does not repress the methionine adenosyltransferase or other methionine biosynthetic enzymes tested.
mesh_terms: D000255:Adenosine Triphosphate; D002250:Carbon Radioisotopes; D003470:Culture Media; D004790:Enzyme Induction; D004794:Enzyme Repression; D006710:Homocysteine / Q000378:metabolism; D008715:Methionine / Q000096:biosynthesis* / Q000378:metabolism; D008780:Methyltransferases / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000378:metabolism; D012436:S-Adenosylmethionine / Q000096:biosynthesis*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology*; D013997:Time Factors
chemical_list: D002250:Carbon Radioisotopes; D003470:Culture Media; D006710:Homocysteine; D012436:S-Adenosylmethionine; D000255:Adenosine Triphosphate; D008715:Methionine; D008780:Methyltransferases; D009713:Nucleotidyltransferases