PYRUVATE-CARBOXYLASE FROM THIOBACILLUS-NOVELLUS - PROPERTIES AND POSSIBLE FUNCTION
PYRUVATE-CARBOXYLASE FROM THIOBACILLUS-NOVELLUS - PROPERTIES AND POSSIBLE FUNCTION
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DOI：
10.1139/m84-081
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发表时间：
1984-01-01
影响因子：
2.8
通讯作者：
WILLER, DW
中科院分区：
文献类型：
--
作者：
CHARLES, AM;WILLER, DW
丙酮酸羧化酶（EC 6.4.1.1）来自T. novellus（ATCC 8093）是高度纯化的，最适pH为7.6，最适温度为25 ℃。35.degree. C以及需要单价和二价阳离子和CoA衍生物以获得最大活性。K+、Mg 2+和乙酰辅酶A对这些作用最好。丙酮酸盐、ATP、HCO 3-和Mg 2+的Km值分别为0.25、0.04、0.27和0.44 mM。增加乙酰辅酶A浓度的初始速度图给出S形曲线，Ka为4.2 μ M，希尔系数为2.2。固定的乙酰辅酶A浓度对不同浓度的丙酮酸、ATP或CO2的曲线都给出了矩形双曲线。除了最终产物，只有氢化甘草酸是抑制性的。这种酶对汞非常敏感。这种酶不被认为具有回补功能，因为在生物体中同时存在高度调节的磷酸烯醇式丙酮酸羧化酶。它可以起到向柠檬酸循环提供草酰乙酸的作用，或者作为提供还原NADP+的系统的一部分。
Pyruvate carboxylase (EC 6.4.1.1) from T. novellus (ATCC 8093) was highly purified and had a pH optimum of 7.6, a temperature optimum of 25.degree.-35.degree. C and a requirement for a monovalent and a divalent cation and a CoA derivative for maximum activity. These were best served by K+, Mg2+ and acetyl-CoA. Km values for pyruvate, ATP, HCO3- and Mg2+ were 0.25, 0.04, 0.27 and 0.44 mM, respectively. Initial velocity plots of increasing acetyl-CoA concentrations gave a sigmoidal curve with Ka of 4.2 .mu.M and Hill coefficients of 2.2. Plots of fixed acetyl-CoA concentrations against varying concentrations of pyruvate, ATP or CO2 all gave rectangular hyperbolae. Apart from end products, only hydropyruvic acid was inhibitory. The enzyme was very sensitive to mercurials. This enzyme is not believed to serve an anaplerotic function because of the simultaneous presence of the highly regulated phosphoenolpyruvate carboxylase in the organism. It may function to supply oxaloacetate to the citrate cycle or as part of the system that provides reduced NADP+.