Waggoner D W, Gómez-Muñoz A, Dewald J, Brindley D N
Signal Transduction Laboratories, Lipid and Lipoprotein Research Group, University of Alberta, 357 Heritage Medical Research Centre, Edmonton, Alberta T6G 2S2, Canada.
J Biol Chem. 1996 Jul 12;271(28):16506-9. doi: 10.1074/jbc.271.28.16506.
A Mg2+-independent phosphatidate phosphohydrolase was purified from rat liver plasma membranes in two distinct forms, an anionic protein and a cationic protein. Both forms of the enzyme dephosphorylated phosphatidate, ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate. When assayed at a constant molar ratio of lipid to Triton X-100 of 1:500, the apparent Km values of the anionic phosphohydrolase for the lipid substrates was 3.5, 1.9, 0.4, and 4.0 microM, respectively. The relative catalytic efficiency of the enzyme for phosphatidate, ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate was 0.16, 0.14, 0.48, and 0.04 liter (min x mg)-1, respectively. The hydrolysis of phosphatidate was inhibited competitively by ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate. The Ki(app) values were 5.5, 5.9, and 4.0 microM, respectively. The hydrolysis of phosphatidate by the phosphohydrolase conformed to a surface dilution kinetic model. It is concluded that the enzyme is a lipid phosphomonoesterase that could modify the balance of phosphatidate, ceramide 1-phosphate, lysophosphatidate, and sphingosine 1-phosphate relative to diacylglycerol, ceramide, monoacylglycerol, and sphingosine, respectively. The enzyme could thus play an important role in regulating cell activation and signal transduction.
从大鼠肝脏质膜中纯化出一种不依赖镁离子的磷脂酸磷酸水解酶，有两种不同形式，一种是阴离子蛋白，另一种是阳离子蛋白。这两种形式的酶都能使磷脂酸、神经酰胺1 - 磷酸、溶血磷脂酸和鞘氨醇1 - 磷酸去磷酸化。当以脂质与Triton X - 100的摩尔比为1:500进行测定时，阴离子磷酸水解酶对脂质底物的表观Km值分别为3.5、1.9、0.4和4.0微摩尔。该酶对磷脂酸、神经酰胺1 - 磷酸、溶血磷脂酸和鞘氨醇1 - 磷酸的相对催化效率分别为0.16、0.14、0.48和0.04升（分钟×毫克）-1。神经酰胺1 - 磷酸、溶血磷脂酸和鞘氨醇1 - 磷酸竞争性抑制磷脂酸的水解。其表观Ki值分别为5.5、5.9和4.0微摩尔。磷酸水解酶对磷脂酸的水解符合表面稀释动力学模型。得出的结论是，该酶是一种脂质磷酸单酯酶，可分别改变磷脂酸、神经酰胺1 - 磷酸、溶血磷脂酸和鞘氨醇1 - 磷酸相对于二酰基甘油、神经酰胺、单酰基甘油和鞘氨醇的平衡。因此，该酶在调节细胞活化和信号转导中可能起重要作用。
