Oil biosynthesis in microsomal membrane preparations from Mortierella alpina

Microsomal membrane preparations from Mortierella alpina catalysed the conversion of sn-glycerol 3-phosphate and [(14)C]oleoyl-CoA to radioactive phosphatidic acid, diacylglycerol and triacylglycerol. Experiments with lysophosphatidic acid and [(14)C]oleoyl-CoA gave a similar pattern of radioactivity in the complex lipids. The specific activity of lysophosphatidate acyltransferase was almost eight times greater than sn-glycerol-3-phosphate acyltransferase, indicating that the first acylation step was limiting in oil assembly in the microsomal membranes. Little conversion of radioactive oleate into phosphatidylcholine occurred, suggesting that triacylglycerol assembly and its relationship to phosphatidylcholine metabolism differed to that found in oilseeds.