Stafforini D M, Rollins E N, Prescott S M, McIntyre T M
Nora Eccles Harrison Cardiovascular Research and Training Institute, Salt Lake City, Utah.
J Biol Chem. 1993 Feb 25;268(6):3857-65.
Platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3- phosphocholine) is a biologically active phospholipid. Tissues, blood cells, and plasma contain PAF acetylhydrolases (calcium independent phospholipase A2 activities) that catalyze the hydrolysis of phospholipids containing short chain sn-2 acyl groups. They inactivate PAF and thereby determine PAF accumulation. We purified the PAF acetylhydrolase from human erythrocytes 15,600-fold. The enzyme has a molecular weight of 25,000, it behaves as a dimer during gel filtration, and it is a previously uncharacterized cytosolic esterase, as it has a unique amino-terminal sequence. The erythrocyte PAF acetylhydrolase requires the addition of sulfhydryl agents for maximal activity, is inhibited by 5,5'-dithiobis(2-nitrobenzoic acid), NaF, diisopropyl fluorophosphate, diethylpyrocarbonate, p-bromophenacylbromide, and a number of proteases. Antibodies against the purified protein precipitate all PAF hydrolase activity from erythrocyte lysates. The erythrocyte PAF acetylhydrolase is specific for short or oxidized sn-2 acyl residues. It exhibits surface dilution kinetics, suggesting that hydrolysis occurs at lipid interfaces. This suggests that this enzyme acts in vivo as a scavenger of oxidatively fragmented phospholipids that are toxic to the cell.
血小板活化因子（PAF，1-O-烷基-2-乙酰基-sn-甘油-3-磷酸胆碱）是一种生物活性磷脂。组织、血细胞和血浆中含有PAF乙酰水解酶（不依赖钙的磷脂酶A2活性），可催化含有短链sn-2酰基的磷脂水解。它们使PAF失活，从而决定PAF的积累。我们从人红细胞中纯化PAF乙酰水解酶达15600倍。该酶分子量为25000，在凝胶过滤过程中表现为二聚体，是一种以前未被鉴定的胞质酯酶，因为它具有独特的氨基末端序列。红细胞PAF乙酰水解酶需要添加巯基试剂才能达到最大活性，受到5,5'-二硫代双（2-硝基苯甲酸）、氟化钠、二异丙基氟磷酸酯、焦碳酸二乙酯、对溴苯甲酰溴和多种蛋白酶的抑制。针对纯化蛋白的抗体可沉淀红细胞裂解物中的所有PAF水解酶活性。红细胞PAF乙酰水解酶对短链或氧化的sn-2酰基残基具有特异性。它表现出表面稀释动力学，表明水解发生在脂质界面。这表明该酶在体内作为对细胞有毒的氧化破碎磷脂的清除剂发挥作用。
