Multiple Enzymic Activities of the Human Cytosolic 85-kDa Phospholipase A2: Hydrolytic Reactions and Acyl Transfer to Glycerol
作者:Arthur M. Hanel、Michael H. Gelb
DOI:10.1021/bi00024a004
日期:1995.6.20
incorporated into 1,2-ditetradecyl-sn-glycero-3-phosphomethanol/Triton X-100 mixed micelles as substrates for the transacylation/hydrolysis reactions of the enzyme. Average product ratios, which are defined as the amount of monoacylglycerol formed to phenyl ester hydrolyzed, were 2.1 +/- 0.1 (n = 5) for the para-substituted phenyl esters and 2.0 +/- 0.3 (n = 7) for phenyl alpha-linolenate. The similarity of
当在甘油存在下进行测定时,重组人85 kDa胞质磷脂酶A2(cPLA2)除了水解这些底物外,还催化了放射性标记的磷脂酰胆碱和脂肪酸的对位取代苯基酯的酰基链向甘油的转移。转酰化反应的产物是单酰基甘油(MAG),且酰基链主要被酯化(>或= 95%)为甘油的伯羟基(sn-1 / 3);立体化学未知。通过为酶-底物复合物形成产物提供额外的机械途径,以及通过增加酶的固有水解和转酰化活性,甘油的浓度都加速了酶的转化。测定了sn-1 / 3-花生四烯酸单酰基甘油的明显酶水解,而sn-1 /3-α-亚麻酸-和sn-2-花生四烯酸单酰基甘油未检测到水解。1,3-丙二醇也可作为酶的酰基受体。cPLA2水解缺少sn-2羟基的溶血磷脂酰胆碱的类似物。该酶将水解rac-1-(花生四烯基,α-亚麻酸,棕榈酰)-2-O-十六烷基-甘油-3-磷酸胆碱脂质的sn-1-酰基链,并将该酰基链转移至甘油。因此,cPLA2具有磷脂