The acylation of sn-glycerol 3-phosphate in mammalian organs and Ehrlich ascites tumor cells.

Abstract

The properties of acyl-CoA:sn-glycerol-3-phosphate acyltransferase in mitochondrial and microsomal fractions from liver and other organs of rat, mouse, guinea pig, rabbit, and beef are described.In liver of all species, the specific activity of the mitochondrial and microsomal enzyme is similar, whereas in other organs the microsomal enzyme is at least 10 times more active.In all types of mitochondria the enzyme shows a strong preference for palmityl-CoA, is insensitive to N-ethylmaleimide, and produces monoacylglycerophosphate as a major product.Microsomal preparations, by contrast, catalyze the acylation of glycerophosphate with both palmityl-CoA and oleyl-CoA, are almost completely inhibited by N-ethylmaleimide, and produce diacylglycerophosphate as the chief reaction product.These criteria, as well as striking differences in response to acetone, are also used to characterize mitochondrial and microsomal associated activities in Ehrlich ascites tumor cells.The properties of the enzyme in the mitochondrial fraction of Ehrlich cells resemble those of its microsomal counterpart.Subcellular distribution studies, using marker enzymes, indicate that glycerophosphate acyltransferase activity in these cells is confined to the microsomes.Taken together, the results raise the possibility that the absence of the acyl-CoA-specific mitochondrial enzyme may have a bearing on the unusual positioning of saturated fatty acids found in certain phospholipids in these tumor cells.Additional experiments indicate that, regardless of whether palmityl-CoA or oleyl-CoA is used as acyl donor, 1-acyl-sn-glycerol 3-phosphate is the major, if not sole product of sn-glycerol a-phosphate acylation in rat liver mitochondria and microsomes as well as in Ehrlich tumor cell microsomes.