title: Characterization of phosphatidylserine synthase from Saccharomyces cerevisiae and a mutant defective in the enzyme.
abstract: The membrane fraction of exponentially growing cells of Saccharomyces cerevisiae was found to exhibit phosphatidylserine synthase activity. The enzyme was solubilized by Triton X-100 and chromatographed on a Sepharose 6B column. The enzyme had a pH optimum between 8.0 and 8.5. The apparent Km values for CDPdiacylglycerol and L-serine were 0.12 and 13 mM, respectively. Triton X-100 stimulated the enzyme. Mg2+ or Mn2+ was required for the activity. Ca2+ was inhibitory at relatively low concentrations. The enzyme was highly specific to L-serine. Labeling experiments showed that the enzyme synthesized phosphatidylserine by transferring the phosphatidyl moiety to L-serine. A mutant of S. cerevisiae defective in phosphatidylserine synthase was isolated. The strain required ethanolamine for its growth. Ethanolamine could be substituted by choline or high concentrations of L-serine. The mutant showed normal levels of CDPdiacylglycerol-inositol 3-phosphatidyltransferase and phosphatidylethanolamine methyltransferase activities.
mesh_terms: D010717:CDPdiacylglycerol-Serine O-Phosphatidyltransferase / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002413:Cations, Divalent; D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D009154:Mutation; D010770:Phosphotransferases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D014166:Transferases / Q000378:metabolism
chemical_list: D002413:Cations, Divalent; D014166:Transferases; D010770:Phosphotransferases; D010717:CDPdiacylglycerol-Serine O-Phosphatidyltransferase