Acylation of sn-glycerol 3-phosphate by cell fractions of rat liver.

The esterification of sn-glycerol 3-(dihydrogen phosphate) with long-chain fatty acids by rat liver microsomal preparations has been studied. A newly modified spectrophotometric assay for glycerolphosphate acyltransferase (GP-acyltransferase) compared favorably with other assay methods, including measurement of the incorporation of sn-glycerol-(14)C 3-(dihydrogen phosphate) into glycerolipids. Cofactor requirements, preliminary kinetic constants, and optimum pH were determined. The product of the reaction was identified as monoacylglycerophosphate by thin-layer chromatography. Albumin activated GP-acyltransferase at low concentrations of acyl CoA but was inhibitory at higher concentrations. Serum -lipoprotein also caused activation of GP-acyltransferase. The effect of albumin could not be attributed to binding of substrate or fatty acids or the provision of metal ions. Diacylglycerophosphate, cytidine triphosphate, sulfhydryl binding agents, and sodium palmitate were identified as inhibitors of microsomal GP-acyltransferase. The physiological significance of these inhibitors remains to be established.