The intrinsic ATPase activity of protein kinase C is catalyzed at the active site of the enzyme.
The intrinsic ATPase activity of protein kinase C is catalyzed at the active site of the enzyme.
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蛋白激酶 C 的内在 ATP 酶活性在酶的活性位点被催化。
作者：
N. Ward;C. O'brian
我们最近报道，自磷酸化蛋白激酶C（PKC）具有内在的Ca（2+）和磷脂依赖性ATP酶活性，并且PKC的ATP酶和组蛋白激酶活性具有相似的金属离子辅因子要求和Km，app（ATP）值。我们推测PKC的内在ATP酶活性可能代表其蛋白激酶活性的键断裂步骤。ATP酶反应的速率比组蛋白激酶反应的速率慢几倍。在亚饱和浓度下，各种肽和蛋白质底物刺激ATP酶反应多达1.5倍。相反，不可磷酸化的底物类似物不是刺激性的。这些观察结果支持PKC催化的一种机制，其中磷酸受体底物的生产性结合增强了PKC活性位点处磷酸供体底物（ATP）水解的速率。然而，这一机制包含一个假设，即PKC的ATP酶活性是在活性位点催化的。事实上，序列分析表明PKC在其活性位点外含有潜在的第二个核苷酸结合位点。在这份报告中，我们提供了一个详细的分析PKC的活性位点和酶的内在ATP酶活性之间的关系。我们发现，三种PKC同工酶的ATP酶反应的调节和催化特性是相似的，尽管在其潜在的非活性位点的核苷酸结合位点在其催化结构域的共识序列的同工酶之间的关键差异。我们还表明，每种同工酶的ATP酶和组蛋白激酶反应具有相似的Km，app（ATP）值。（250字处删节）
We recently reported that autophosphorylated protein kinase C (PKC) has an intrinsic Ca(2+)- and phospholipid-dependent ATPase activity and that the ATPase and histone kinase activities of PKC have similar metal-ion cofactor requirements and Km,app(ATP) values. We hypothesized that the intrinsic ATPase activity of PKC may represent the bond-breaking step of its protein kinase activity. The rate of the ATPase reaction is several times slower than the histone kinase reaction rate. At subsaturating concentrations, various peptide and protein substrates stimulate the ATPase reaction by as much as 1.5-fold. In contrast, non-phosphorylatable substrate analogs are not stimulatory. These observations support a mechanism of PKC catalysis in which the productive binding of phosphoacceptor substrates enhances the rate of phosphodonor substrate (ATP) hydrolysis at the active site of PKC. However, this mechanism contains an assumption that the ATPase activity of PKC is catalyzed at the active site. In fact, sequence analysis indicates that PKC contains a potential second nucleotide binding site outside of its active site. In this report, we provide a detailed analysis of the relationship between the active site of PKC and the intrinsic ATPase activity of the enzyme. We show that the regulatory and catalytic properties of the ATPase reactions of three PKC isozymes are similar, despite critical differences among the isozymes in their consensus sequences for the potential non-active-site nucleotide binding site in their catalytic domains. We also show that the ATPase and histone kinase reactions of each isozyme have similar Km,app(ATP) values.(ABSTRACT TRUNCATED AT 250 WORDS)
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DOI：
--
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影响因子：
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DOI：
--
发表时间：
1991
期刊：
The Journal of biological chemistry
影响因子：
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作者：
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