Yanoshita R, Kudo I, Ikizawa K, Chang H W, Kobayashi S, Ohno M, Nojima S, Inoue K
Faculty of Pharmaceutical Sciences, University of Tokyo.
J Biochem. 1988 May;103(5):815-9. doi: 10.1093/oxfordjournals.jbchem.a122352.
We examined the substrate specificity of PAF-degrading enzymes from various sources using platelet activating factor (PAF) and its synthetic analogs. The results were as follows: 1) Tissue-originated acetylhydrolases, such as rat kidney soluble enzyme, deacetylated 1S-methyl-1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine (1S-Me-PAF) slightly more rapidly than PAF, whereas plasma acetylhydrolase hydrolyzed PAF more effectively than 1S-Me-PAF. 2) Rat polymorphonuclear leukocytes, monocytes, and lymphocytes homogenates showed an appreciable acetylhydrolase activity, the substrate specificity of which resembled that of the plasma enzyme. 3) Pleural exudates in an experimental pleurisy induced in rats by carrageenan contained an acetylhydrolase activity, the properties of which were similar to those of the plasma enzyme. 4) An extracellular phospholipase A2 activity, which was also observed in the pleural exudate and required Ca2+ ion for maximum activity, seemed not to participate in the deacetylation of PAF, since addition of EDTA did not affect the PAF deacetylation catalyzed by the pleural exudate. These findings indicate that the inactivation reaction of PAF present in the extracellular space is mainly catalyzed by plasma acetylhydrolase, which yields lysoPAF.
我们使用血小板活化因子（PAF）及其合成类似物研究了来自各种来源的PAF降解酶的底物特异性。结果如下：1）组织来源的乙酰水解酶，如大鼠肾可溶性酶，使1S-甲基-1-O-十六烷基-2-乙酰基-sn-甘油-3-磷酸胆碱（1S-Me-PAF）脱乙酰化的速度比PAF略快，而血浆乙酰水解酶水解PAF的效率比1S-Me-PAF更高。2）大鼠多形核白细胞、单核细胞和淋巴细胞匀浆显示出明显的乙酰水解酶活性，其底物特异性与血浆酶相似。3）角叉菜胶诱导的大鼠实验性胸膜炎中的胸腔渗出液含有乙酰水解酶活性，其性质与血浆酶相似。4）在胸腔渗出液中也观察到的一种细胞外磷脂酶A2活性，其最大活性需要Ca2+离子，似乎不参与PAF的脱乙酰化，因为添加EDTA不影响胸腔渗出液催化的PAF脱乙酰化。这些发现表明，细胞外空间中PAF的失活反应主要由血浆乙酰水解酶催化，生成溶血PAF。
