PHOSPHOLIPID-SYNTHESIZING ENZYMES IN GOLGI MEMBRANES OF THE YEAST, SACCHAROMYCES-CEREVISIAE

Golgi membranes of the yeast, Saccharomyces cerevisiae, mere isolated by a method similar to the procedure described by Cleves et al. [Cell 64 (1991) 789-800]. Marker proteins of the Golgi, such as Kex2 proteas e and GDPase, are highly enriched in these preparations, The phospholi pid and ergosterol content of Golgi membranes is low, Phosphatidylchol ine, phosphatidylethanolamine, and phosphatidylinositol are the major phospholipids of this compartment. The amount of phosphatidylserine in the Golgi is significantly higher than in yeast bulk membranes, Inosi tol-containing sphingolipids, especially inositolphosphorylceramide, a re highly enriched in Golgi membranes, Two phospholipid-synthesizing e nzymes, namely phosphatidylinositol synthase and sn-1,2-diacylglycerol cholinephosphotransferase, are detected in the Golgi at a specific ac tivity which exceeds that of the endoplasmic reticulum.