Lysophospholipase and the metabolism of lysophosphatidylcholine in isolated bovine rod outer segments.
Incubation of bovine rod outer segments (ROS) with radiolabeled palmitic acid (16:0) and lysophosphatidylcholines (lysoPC) radiolabeled in either the fatty acid or the choline group indicated the presence of a lysophospholipase activity that is unaffected by Ca2+. In the presence of ATP, Mg2+ and CoA and acyl CoA:lysophospholipid acytransferase activity is evident, and free fatty acids, including those released by lysophospholipase activity, are esterified to membrane phospholipids. At low concentrations of lysoPC, 68% of it is acylated to form phosphatidylcholine (PC) and 24% is converted to glycerophosphocholine (GPC) and fatty acid per hour. As the concentration of lysoPC increases lysophospholipase activity increases, acyl-CoA:lysophospholipid acyltransferase activity decreases, and the proportion of lysoPC converted to PC decreases. The rate of production of lysophospholipids in vitro under phospholipase A-stimulatory conditions exceeds the rate at which it can be removed by 5-10-fold. This suggests the possibility that an early step in light, anoxia- or hypoxia-induced damage to photoreceptor cells may be activation of the phospholipase A endogenous to ROS.
Zimmerman
W F
WF
Department of Biology, Amherst College, MA 01002.
Keys
S
S
D008243:1-Acylglycerophosphocholine O-Acyltransferase / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D003065:Coenzyme A / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005997:Glycerylphosphorylcholine / Q000378:metabolism; D008244:Lysophosphatidylcholines / Q000378:metabolism*; D008245:Lysophospholipase / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism; D010169:Palmitic Acids / Q000378:metabolism; D010713:Phosphatidylcholines / Q000096:biosynthesis; D010740:Phospholipases / Q000378:metabolism*; D010767:Phosphorylcholine / Q000378:metabolism; D010786:Photoreceptor Cells / Q000201:enzymology*; D012374:Rod Cell Outer Segment / Q000201:enzymology*; D013997:Time Factors
D005227:Fatty Acids; D008244:Lysophosphatidylcholines; D010169:Palmitic Acids; D010713:Phosphatidylcholines; D010767:Phosphorylcholine; D005997:Glycerylphosphorylcholine; D000255:Adenosine Triphosphate; D008243:1-Acylglycerophosphocholine O-Acyltransferase; D010740:Phospholipases; D008245:Lysophospholipase; D008274:Magnesium; D003065:Coenzyme A