Shetty K T
Department of Neurochemistry, National Institute of Mental Health and Neuro Sciences, Bangalore, India.
Neurochem Res. 1990 Dec;15(12):1203-10. doi: 10.1007/BF01208581.
Phosphoserine phosphatase (PSPase), a cytosolic enzyme has been purified 106 fold from human brain, by employing conventional protein purification techniques. The use of MgCl2 (10 mM) and chloroform treatment, during purification enabled the removal of non-specific proteins. The final enzyme preparation exhibited a broad pH optimum of 5.6-6.6 and could dephosphorylate both L and D enantiomers of the phosphoserine, but with different Km values for O-P-L serine (3.6 x 10(-5) M) and O-P-D serine (1 x 10(-4) M). Enzyme activity was found to be specific for phosphoserine, whereas other phosphoesters including phosphothreonine and phosphoproteins such as casein and phosvitin were found to be poor substrates. The enzyme activity was uncompetitively inhibited by L-serine. Further the PSPase activity was inhibited by vanadate, (41%), trifluoperazine (23%), chlorpromazine (34%) at an equimolar concentration of 1 mM, whereas lithium and ethanol did not influence the enzyme activity. Minor tranquilizers such as diazepam and chlordiazepoxide activated the enzyme activity to an extent of 13% and 59% respectively. In addition, species and regionwise heterogeneity was observed with respect to distribution of enzyme activity in six major areas of human, rabbit and rat brains.
磷酸丝氨酸磷酸酶（PSPase）是一种胞质酶，通过采用传统蛋白质纯化技术，已从人脑组织中纯化了106倍。在纯化过程中使用MgCl2（10 mM）和氯仿处理，能够去除非特异性蛋白质。最终的酶制剂在pH 5.6 - 6.6范围内表现出较宽的最适pH值，并且能够使磷酸丝氨酸的L型和D型对映体去磷酸化，但对O-P-L丝氨酸（3.6 x 10(-5) M）和O-P-D丝氨酸（1 x 10(-4) M）具有不同的Km值。发现该酶活性对磷酸丝氨酸具有特异性，而其他磷酸酯，包括磷酸苏氨酸以及酪蛋白和卵黄高磷蛋白等磷蛋白，被发现是较差的底物。该酶活性受到L-丝氨酸的非竞争性抑制。此外，在1 mM等摩尔浓度下，钒酸盐（41%）、三氟拉嗪（23%）、氯丙嗪（34%）对PSPase活性有抑制作用，而锂和乙醇不影响酶活性。地西泮和氯氮卓等弱安定剂分别使酶活性激活了13%和59%。此外，在人、兔和大鼠脑的六个主要区域中，观察到酶活性分布存在物种和区域异质性。
