title: Regulatory properties of O-acetyl-L-serine sulfhydrylase of Cephalosporium acremonium: evidence of an isoenzyme and its importance in cephalosporin C biosynthesis.
abstract: O-Acetyl-L-serine sulfhydrylase catalyzes the final step in the biosynthesis of cysteine from H2S and O-acetyl-L-serine in the fungus Cephalosporsium acremonium, a cephalosporin C-producing organism. We separated this enzyme from the closely related but less specific O-acetyl-L-homoserine sulfhydrylase and showed that O-acetyl-L-homoserine sulfhydrylase also catalyzes the formation of cysteine from O-acetyl-L-serine and H2S. The expression of O-acetyl-L-serine sulfhydrylase was regulated by exogenous methionine. In addition, this enzyme was inhibited by S-adenosyl-L-methionine and 5-formylpteroyl monoglutamic acid. The inhibition of both S-adenosyl-L-methionine and 5-formylpteroyl monoglutamic acid was noncompetitive. Results obtained with gel filtraton experiments in various buffer systems indicate an association-dissociation behavior of O-acetyl-L-serine sulfhydrylase.
mesh_terms: D000164:Acremonium / Q000201:enzymology* / Q000378:metabolism; D002511:Cephalosporins / Q000096:biosynthesis*; D002850:Chromatography, Gel; D003545:Cysteine / Q000096:biosynthesis; D003547:Cysteine Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D008190:Lyases / Q000378:metabolism*; D008715:Methionine / Q000494:pharmacology; D009154:Mutation; D012436:S-Adenosylmethionine / Q000494:pharmacology; D013997:Time Factors
chemical_list: D002511:Cephalosporins; D007527:Isoenzymes; C025163:cephalosporin C; D012436:S-Adenosylmethionine; D008715:Methionine; D003547:Cysteine Synthase; D008190:Lyases; D003545:Cysteine