The human monocyte cell line U937 expresses phospholipase A2 and phospholipase C activities and produces eicosanoids. The phospholipase C (PLC) activity exhibits substrate preference for phosphatidyl-choline (PC), rather than phosphatidylinositol or phosphatidylethanolamine. In order to characterize the PLC activity found in these cells, the effects of substitution of the sn-2 fatty acid on this activity were examined. PC substrates with palmitic acid (PC-2P), oleic acid (PC-2O), arachidonic acid (PC-2A) and linoleic acid (PC-2L) at the sn-2 position were used. The sn-1 fatty acid was palmitic acid. PC-2L and PC-2A with the longer-chain less-saturated fatty acids linoleic acid and arachidonic acid esterified at sn-2 were found to be better substrates for PLC activity than PC-2P or PC-2O in these cells. This preference was maintained even when substrate phospholipid was solubilized in non-ionic, anionic, cationic and zwitterionic amphiphiles. Furthermore, when a 500-fold excess of 1,2-diolein or 1,2-dipalmitin was added to the reaction, the specificity of the PLC activity for PC-2A and PC-2L remained unchanged. When similar experiments were performed with phosphatidylinositol as a substrate, we did not observe any effect when the sn-2 position was altered. These data show that the fatty acid constituent at the sn-2 position affects the observed PLC activity when phosphatidylcholine, but not phosphatidylinositol, is used as a substrate by these cells.
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Research Article|
June 15 1987
The effect of sn-2 fatty acid substitution on phospholipase C enzyme activities
J S Bomalaski;
J S Bomalaski
1Department of Medicine, Philadelphia Veterans Administration Medical Center, PA 19104.
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M A Clark
M A Clark
1Department of Medicine, Philadelphia Veterans Administration Medical Center, PA 19104.
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1987 London: The Biochemical Society
1987
Biochem J (1987) 244 (3): 497–502.
Citation
J S Bomalaski, M A Clark; The effect of sn-2 fatty acid substitution on phospholipase C enzyme activities. Biochem J 15 June 1987; 244 (3): 497–502. doi: https://doi.org/10.1042/bj2440497
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