Distribution of membrane marker enzymes in cultured arterial endothelial and smooth muscle cells. The subcellular location of oleoyl-CoA:1-acyl-sn-glycero-3-phosphocholine acyltransferase.

The subcellular distribution of oleoyl-CoA:1-acyl-sn-glycero-3-phosphocholine acyltransferase (E.C.2.3.1.23) in cultured swine aorta endothelial cells and smooth muscle cells was investigated. Isolated membrane pellets were centrifuged through linear sucrose gradients, and the distributions of the activities of seven membrane-bound enzymes were measured. The distribution of acyltrasferase activity was similar to that of the endoplasmic reticulum enzymes. Gradient fractions which contained intact mitochondria had very low activities of acyltransferase. Experiments using mixed fractions and measurements made under conditions which inhibit phospholipase A2 showed that no acyltransferase activity from this location was masked by competing activities. When membranes were treated with digitonin, plasma membranes specifically increased in density, facilitating their separation from endoplasmic reticulum membranes. The plasma membranes were free of acyltransferase activity. We conclude that in cultured swine arterial smooth muscle and endothelial cells, acyltransferase is located primarily in the endoplasmic reticulum.