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Acyl specificity of phospholipases A2 and C in thrombin-stimulated human platelets
Yoseph Tsegaye1, Knut Olav Daasvatn, Holm Holmsen
1Department of Biochemistry and Molecular Biology, University of Bergen, Bergen, Norway.
Abstract:
Platelets were labelled separately with six different, radioactive unsaturated fatty acids. The cells were isolated from the radioactive precursors and treated with and without 2 U/ml of thrombin. The formation of radioactive free fatty acid+oxygenated fatty acids and of radioactive radioactive phosphatidic acid+diacylglycerol was taken as a measure of the PLA(2) and PLC reactions, respectively. We found that that in intact platelets PLA(2) prefers phospholipid molecular species containing unsaturated acyls, most likely in the sn-2 position, in the priority order: 20:4>20:5>18:2 = 18:3 = 22:6>>18:1, while PLC prefers its substrates in the priority order 20:5>20:4>18:2>18:3 = 22:6>18:1.