Acyl-CoA:lysophosphatidylcholine Acyltransferase Activity in Bovine Retina Rod Outer Segments

In the present paper the properties of acyl-CoA:lysophosphatidylcholine acyltransferase activity associated with rod outer segments (ROS) have been studied. Under adequate experimental conditions, ROS acyl-CoA:lysophosphatidylcholine acyltransferase activity presented a maximum at pH 7.0. The enzyme was able to incorporate as much as 60% of the label offered as [1-14C]oleoyl-CoA into phosphatidylcholine after 5 min of incubation. The use of varying concentrations of oleoyl-CoA and 46 μmlysophosphatidylcholine gave an apparentKmvalue for oleoyl-CoA of 100 μmand aVmaxvalue of 153 nmol × h−1× (mg protein)−1. The use of varying concentrations of lysophosphatidylcholine and 100 μmoleoyl-CoA gave an apparentKmvalue for lysophosphatidylcholine of 27 μmand aVmaxvalue of 155 nmol × h−1× (mg protein)−1. The enzyme was inhibited by 25% when ROS membranes were incubated in the presence of 10 mmMgCl2. The acyltransferase was able to incorporate other acyl-CoAs (palmitoyl-CoA and arachidonoyl-CoA) into ROS phospholipids and to acylate other lysophospholipids but less efficiently than lysophosphatidylcholine. Lysophoshatidylcholine was preferentially acylated with arachidonic acid followed by oleic acid and, less efficiently, with palmitic acid.The high specific activity of acyl-CoA lysophosphatidylcholine acyltransferase found in purified ROS compared to the activity found in other subcellular fractions of the bovine retina suggests that this enzymatic activity is native to the ROS.