title: Role of Saccharomyces cerevisiae serine O-acetyltransferase in cysteine biosynthesis.
abstract: Some strains of Saccharomyces cerevisiae have detectable activities of L-serine O-acetyltransferase (SATase) and O-acetyl-L-serine/O-acetyl-L-homoserine sulfhydrylase (OAS/OAH-SHLase), but synthesize L-cysteine exclusively via cystathionine by cystathionine beta-synthase and cystathionine gamma-lyase. To untangle this peculiar feature in sulfur metabolism, we introduced Escherichia coli genes encoding SATase and OAS-SHLase into S. cerevisiae L-cysteine auxotrophs. While the cells expressing SATase grew on medium lacking L-cysteine, those expressing OAS-SHLase did not grow at all. The cells expressing both enzymes grew very well without L-cysteine. These results indicate that S. cerevisiae SATase cannot support L-cysteine biosynthesis and that S. cerevisiae OAS/OAH-SHLase produces L-cysteine if enough OAS is provided by E. coli SATase. It appears as if S. cerevisiae SATase does not possess a metabolic role in vivo either because of very low activity or localization. For example, S. cerevisiae SATase may be localized in the nucleus, thus controlling the level of OAS required for regulation of sulfate assimilation, but playing no role in the direct synthesis of L-cysteine.
authors.affiliation: Department of Bioscience, Fukui Prefectural University, 4-1-1 Kenjojima, Matsuoka-cho, 910-1195, Fukui, Japan. hiro@fpu.ac.jp
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takagi
authors.forename: Kenji
authors.initials: K
authors.lastname: Yoshioka
authors.forename: Naoki
authors.initials: N
authors.lastname: Awano
authors.forename: Shigeru
authors.initials: S
authors.lastname: Nakamori
authors.forename: Bun ichiro
authors.initials: Bi
authors.lastname: Ono
mesh_terms: D000123:Acetyltransferases / Q000037:antagonists & inhibitors / Q000502:physiology*; D019757:Carbon-Oxygen Lyases / Q000378:metabolism; D003545:Cysteine / Q000096:biosynthesis*; D003547:Cysteine Synthase; D008190:Lyases / Q000378:metabolism; D009097:Multienzyme Complexes; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D051050:Serine O-Acetyltransferase; D013431:Sulfates / Q000378:metabolism
chemical_list: D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; D013431:Sulfates; D000123:Acetyltransferases; D051050:Serine O-Acetyltransferase; D003547:Cysteine Synthase; C103381:MET17 protein, S cerevisiae; C018725:O-acetylhomoserine (thiol)-lyase; D008190:Lyases; D019757:Carbon-Oxygen Lyases; D003545:Cysteine