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J.Health Sci., 46(4), 275-281, 2000
Enhanced Degradation of Phospholipids by Phospholipase A2 in Liver of Carbon Tetrachloride-Treated Rat
Akemi Ryu,1 Hiroyuki Itabe,2 Mariko Mutoh, Ichiro Kudo,3 Hiroyuki Arai,* and Keizo Inoue
Department of Health Chemistry, Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-0033, Japan
Stimulated phospholipid degradation was observed in liver homogenates harvested from rats who had received an injection of carbon tetrachloride (CCl4). When the liver homogenates obtained from CCl4-treated rats were incubated for 1 h at 37°C, approximately half of the phosphatidylethanolamine (PE) was hydrolyzed, producing a stoichiometrical amount of lysophosphatidylethanolamine (LysoPE). The homogenates obtained from control rats showed only poor hydrolytic activity toward endogenous PE. The fatty acid composition of lysoPE produced was essentially identical to that at the sn-1 position of PE, suggesting that A2 type of phospholipase (PLase A2) was involved in the degradation during incubation. The hydrolysis of endogenous PE was dependent on calcium ion. The hydrolytic activity was almost exclusively associated with the membrane fraction which was precipitated by centrifugation at 10000 × g, and did not require the cytosol fraction. Para-bromophenacylbromide, rabbit antibody against rat 14 kDa type II PLase A2, and thielocin A1, a specific inhibitor of type II PLase A2, suppressed the hydrolysis almost completely. These results indicate that the accelerated degradation of endogenous PE observed in liver homogenates of CCl4-treated rat may be mainly due to the activity of the enzyme closely related to type II PLase A2.
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