Department of Biochemistry, Faculty of Science, Banaras Hindu University, Varanasi-221 005, India.
Plant Physiol. 1990 May;93(1):194-200. doi: 10.1104/pp.93.1.194.
A phosphoenolpyruvate (PEP) phosphatase was purified to homogeneity from germinating mung beans (Vigna radiata). It was found to be a tetrameric protein (molecular mass 240,000 daltons) made up of apparently identical subunits (subunit molecular mass 60,000 daltons). It was free from bound nucleotides. It did not show pyruvate kinase activity. The enzyme showed high specificity for PEP. Pyrophosphate and some esters (nucleoside di- and triphosphates) were hydrolyzed slowly and phosphoric acid monoesters were not hydrolyzed. The enzyme showed maximum activity at pH 8.5. At this pH, the K(m) of PEP was 0.14 millimolar and the V(max) was equal to 1.05 micromoles pyruvate formed per minute per milligram enzyme protein. Dialysis of the enzyme against 10 millimolar triethanolamine buffer (pH 6.5), led to loss of the catalytic activity, which was restored on addition of Mg(2+) ions (K(m) = 0.12 millimolar). Other divalent metal ions inhibited the Mg(2+) -activated enzyme. PEP-phosphatase was inhibited by ATP and several other metabolites.
从发芽绿豆（Vigna radiata）中纯化出一种磷酸烯醇丙酮酸（PEP）磷酸酶，达到均相。它被发现是一种四聚体蛋白（分子量 240,000 道尔顿），由显然相同的亚基（亚基分子量 60,000 道尔顿）组成。它不含结合核苷酸。它没有表现出丙酮酸激酶活性。该酶对 PEP 表现出高特异性。焦磷酸盐和一些酯（核苷二磷酸和三磷酸）缓慢水解，磷酸单酯不水解。该酶在 pH 8.5 时表现出最大活性。在此 pH 值下，PEP 的 K(m)为 0.14 毫摩尔，V(max)等于每分钟每毫克酶蛋白形成 1.05 微摩尔丙酮酸。用 10 毫摩尔三乙醇胺缓冲液（pH 6.5）透析该酶会导致催化活性丧失，而添加 Mg(2+)离子（K(m)=0.12 毫摩尔）会恢复这种活性。其他二价金属离子抑制 Mg(2+)-激活的酶。PEP-磷酸酶被 ATP 和其他几种代谢物抑制。
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