小鼠腹水型肝癌H22a细胞浆内磷蛋白磷酸酶活力调节的研究

小鼠腹水型肝癌细胞胞浆内磷蛋白磷酸酶对磷酸化的组蛋白、酪蛋白、鱼精蛋白具有脱磷酸化活力,而对小分子底物P-Ser、P-Thr、P-Tyr、PNPP等无活力。二价金属离子Mn~(2+)、Co~(2+)、Mg~(2+)对酶有明显激活作用,而Zn~(2+)、F~-、Pi对酶有明显抑制作用。代谢中间物G-6-P、G-1-P、F-6-P、F-1.6-2P、ATP、ADP、GTP对酶有抑制作用,而磷酸化氨基酸和环核苷酸对酶活影响很小。还试验了碱性蛋白质和酸性蛋白质对酶活力的影响,肝素和组蛋白均对酶活力有抑制作用,当两者混和后,其抑制作用会相互抵消。

STUDIES ON ACTIVITY REGULATION OF PHOSPHO-PROTEIN PHOSPHATASE IN CYTOSOL FROMH22a HEPATOMA ASCITES CELLS

The phosphoprotein phosphatase was purified from cytosol of H22a hepatoma ascites cells. It catalyzed the dephosphorylation of the phosphorylated proteins including histones casein and protamine, but not the low molecular weight phosphorylated compounds such as phosphoserine, phosphothreonine,phosphotyrosine and PNPP. It was inhibited strongly by Zn2+,F-,Pi and stimulated significantly by divalent cations Mn2+,Co2+ and Mg2+. Inhibition by the metabolic intermediates such as -glucose-1-phosphate, glucose-6-phosphate, fructose-8-phosphate, fructose-1, 6-di-phosphate, ATP,ADP,GTP was also observed. But phosphorylated amino acids and cyclic nucleotides had little effects on its activity. In this paper the effects of basic proteins, acidic protein on phosphoprotein phosphatase had been tested. It was observed that the activity of enzyme was inhibited by heparin or histone. But when the reaction mixtures contained both heparin and histone, the latter can counteracted with the inhibitory effect of the former.