ACYL-COA-LYSOPHOSPHATIDYLCHOLINE ACYLTRANSFERASE ACTIVITY IN BOVINE RETINA ROD OUTER SEGMENTS

In the present paper the properties of acyl-CoA:lysophosphatidylcholin e acyltransferase activity associated with rod outer segments (ROS) ha ve been studied, Under adequate experimental conditions, ROS acyl-CoA: lysophosphatidylcholine acyltransferase activity presented a maximum a t pH 7.0. The enzyme was able to incorporate as much as 60% of the lab el offered as [1-C-14]oleoyl-CoA into phosphatidylcholine after 5 min of incubation. The use of varying concentrations of oleoyl-CoA and 46 mu M lysophosphatidylcholine gave an apparent K-m value for oleoyl-CoA of 100 mu M and a V-max value of 153 nmol x h(-1) x (mg protein)(-1). The use of varying concentrations of lysophosphatidylcholine and 100 mu M oleoyl-CoA gave an apparent K-m value for lysophosphatidylcholine of 27 mu M and V-max value of 155 nmol x h(-1) x (mg protein)(-1). Th e enzyme was inhibited by 25% when ROS membranes were incubated in the presence of 10 mM MgCl2. The acyltransferase was able to incorporate other acyl-CoAs (palmitoyl-CoA and arachidonoyl-CoA) into ROS phosphol ipids and to acylate other lysophospholipids but less efficiently than lysophosphatidylcholine. Lysophoshatidylcholine was preferentially ac ylated with arachidonic acid followed by oleic: acid and, less efficie ntly, with palmitic acid,The high specific activity of acyl-CoA lysoph osphatidylcholine acyltransferase found in purified ROS compared to th e activity found in other subcellular fractions of the bovine retina s uggests that this enzymatic activity is native to the ROS. (C) 1997 Ac ademic Press.