The acyltransferase activity of adrenal medulla and sacroplasmic reticulum of skeletal muscles.

The presence of acyl-CoA-lysolecithin-acyltransferase was studied in ox adrenal medulla fractionated by sucrose gradient centrifugation. The highest activity of this enzyme is localized in the microsomes and not in the membranes of chromaffin granules. Estimation of acyltransferase activity in fragments of sarcoplasmic reticulum (SR) from rabbit skeletal muscles before and after sucrose gradient centrifugation shows that in these membranes acyltransferase is a membrane bound enzyme. Both enzyme preparations transfer 18-carbon fatty acids in increasing order of unsaturation to 1-acyl-sn-glycer-3-phosphorylcholine (1-acyl-GPC) (18:0 less than 18:1 less than 18:2) and in decreasing order to 2-acyl-sn-glycero-3-phosphorylcholine (2-acyl-GPC) (18:0 greater than 18:1 greater than 18:2). For the acyltransferase present in ox adrenal medulla and fragments of sarcoplasmic reticulum, 1-acyl-sn-glycero-3-phosphorylethanolamine (1-acyl-GPE) is not a good acyl acceptor. The importance of acyltransferase in the de- and re-acylation cycle for the neogenesis of membranes-specific lecithin is discussed.