Role of lipid structure in the activation of phospholipase A2 by peroxidized phospholipids |
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Authors: | Larry R McLean Karen A Hagaman W Sean Davidson |
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Affiliation: | (1) Marion Merrell Dow Research Institute, 2110 East Galbraith Road, 45215 Cincinnati, OH;(2) Present address: Department of Biochemistry, The Medical College of Pennsylvania, 2900 Queen Lane, 19129 Philadelphia, PA |
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Abstract: | The time course of hydrolysis of a mixed phospholipid substrate containing bovine liver 1,2-diacyl-sn-glycero-3-phosphocholine (PC) and 1,2-diacyl-sn-glycero-3-phosphoethanolamine (PE) catalyzed byCrotalus adamanteus phospholipase A2 was measured before and after peroxidation of the lipid substrate. The rate of hydrolysis was increased after peroxidation
by an iron/adenosine diphosphate (ADP) system; the presence of iron/ADP in the assay had a minimal inhibitory effect. The
rate of lipid hydrolysis was also increased after the substrate was peroxidized by heat and O2. Similarly, peroxidation increased the rate of hydrolysis of soy PC liposomes that did not contain PE. In order to minimize
interfacial factors that may result in an increase in rate, the lipids were solubilized in Triton X-100. In mixtures of Triton
with soy PC in the absence of PE, peroxidation dramatically increased the rate of lipid hydrolysis. In addition, the rate
of hydrolysis of the unoxidizable lipid 1-palmitoyl-2-1-14C]oleoyl PC incorporated into PC/PE liposomes was unaffected by peroxidation of the host lipid. These data are consistent
with the notions that the increase in rate of hydrolysis of peroxidized PC substrates catalyzed by phospholipase A2 is due largely to a preference for peroxidized phospholipid molecules as substrates and that peroxidation of host lipid does
not significantly increase the rate of hydrolysis of nonoxidized lipids. |
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