日本血吸虫SjPP基因原核表达蛋白的酶活性

Enzymatic activities of the protein expressed-prokaryoticly in Escherichia coli from SjPP gene of Schistosoma japonicum

分别以磷酸苏氨酸多肽（K-R-pT-I—R—R）和4-硝基苯基磷基二钠盐（pNPP）为底物，研究原核表达的日本血吸虫丝／苏氨酸蛋白磷酸酶重组蛋白rSjPP的酶活性，检测二价金属阳离子（Mn^2＋、Ni^2＋、Mg^2＋、Ca^2＋）、温度、pH值对rSjPP酶活性的影响。结果显示，rSjPP重组蛋白可以有效地水解磷酸苏氨酸多肽，具有丝／苏氨酸蛋白磷酸酶活性。rSjPP酶活性的最适温度为60℃，最适pH值为8．0。1～4mmol／L Ni^2＋对rSjPP酶活力有促进作用，但Mn^2＋、Mg^2＋、Ca^2＋等阳离子对rSjPP的酶活力影响不大。

Using phosphothreonine polypeptide K-R-pT-I-R-R as substrate, the activities of Ser/Thr protein phosphatase （rSjPP） of Schistosoma japonicum expressed in Escherichia coli were tested. The effects of temperature,pH value,divalent cations（Mn^2＋ ,Ni^2＋ ,Mg^2＋ ,and Ca^2＋） on the enzymatic activities of the rSjPP were analyzed using pNPP as substrate. The phosphothreonine polypeptide could been hydrolyzed by the rSjPP,indicating that the rSjPP possessed the characteristics of Ser/Thr protein phosphatase. Using pNPP as substrate,rSjPP had the strongest catalytic activities under the condition of pH8.0 and 60℃. The activities of rSjPP could be enhanced by adding Ni^2＋ from 1 mmol/L to 4 mmol/L but not by Mn^2＋ ,Mg^2＋ ,and Ca^2＋.