Glycerolipid biosynthesis in Saccharomyces cerevisiae: sn-glycerol-3-phosphate and dihydroxyacetone phosphate acyltransferase activities.
Yeast acyl-coenzyme A:dihydroxyacetone-phosphate O-acyltransferase (DHAP acyltransferase; EC 2.3.1.42) was investigated to (i) determine whether its activity and that of acyl-coenzyme A:sn-glycerol-3-phosphate O-acyltransferase (glycerol-P acyltransferase; EC 2.3.1.15) represent dual catalytic functions of a single membranous enzyme, (ii) estimate the relative contributions of the glycerol-P and DHAP pathways for yeast glycerolipid synthesis, and (iii) evaluate the suitability of yeast for future genetic investigations of the eucaryotic glycerol-P and DHAP acyltransferase activities. The membranous DHAP acyltransferase activity showed an apparent Km of 0.79 mM for DHAP, with a Vmax of 5.3 nmol/min per mg, whereas the glycerol-P acyltransferase activity showed an apparent Km of 0.05 mM for glycerol-P, with a Vmax of 3.4 nmol/min per mg. Glycerol-P was a competitive inhibitor (Ki, 0.07 mM) of the DHAP acyltransferase activity, and DHAP was a competitive inhibitor (Ki, 0.91 mM) of the glycerol-P acyltransferase activity. The two acyltransferase activities exhibited marked similarities in their pH dependence, acyl-coenzyme A chain length preference and substrate concentration dependencies, thermolability, and patterns of inactivation by N-ethylmaleimide, trypsin, and detergents. Thus, the data strongly suggest that yeast glycerol-P and DHAP acyltransferase activities represent dual catalytic functions of a single membrane-bound enzyme. Furthermore, since no acyl-DHAP oxidoreductase activity could be detected in yeast membranes, the DHAP pathway for glycerolipid synthesis may not operate in yeast.
D000214:Acyl Coenzyme A / Q000378:metabolism; D000217:Acyltransferases / Q000378:metabolism*; D003840:Deoxycholic Acid / Q000494:pharmacology; D004099:Dihydroxyacetone Phosphate; D005033:Ethylmaleimide / Q000494:pharmacology; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000378:metabolism*; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D010088:Oxidoreductases / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D014357:Trypsin / Q000494:pharmacology
D000214:Acyl Coenzyme A; D003840:Deoxycholic Acid; D011092:Polyethylene Glycols; D004099:Dihydroxyacetone Phosphate; D010088:Oxidoreductases; D000217:Acyltransferases; D005992:Glycerol-3-Phosphate O-Acyltransferase; D014357:Trypsin; D005033:Ethylmaleimide