Substrate inhibition of the mitochondrial and cytoplasmic malate dehydrogenases.
Substrate inhibition of the mitochondrial and cytoplasmic malate dehydrogenases.
复制标题
线粒体和细胞质苹果酸脱氢酶的底物抑制。
DOI：
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发表时间：
1978
影响因子：
4.8
通讯作者：
J. Everse
中科院分区：
文献类型：
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作者：
L. Bernstein;M. Grisham;K. Cole;J. Everse
用从猪心脏中获得的两种苹果酸脱氢酶同工酶研究了在高浓度底物存在下导致酶活性抑制的机制。抑制作用是由酶和草酸酯的烯醇形式形成的流产二元络合物促进的。氧化辅酶和还原辅酶似乎都没有参与这种复合物的形成。这些结果表明，猪心脏苹果酸脱氢酶对底物的抑制机制与鸡心脏乳酸脱氢酶不同。草草乙酸对线粒体酶的抑制常数为2.0 mM，对细胞质酶的抑制常数为4.5 mM。由于草酸酯的体内浓度据报道约为10微米，这些数据表明，苹果酸脱氢酶所表现出的底物抑制可能在体内没有任何意义。
The mechanism that leads to an inhibition of enzyme activity in the presence of high concentrations of substrate was investigated with the two malate dehydrogenase isoenzymes obtained from pig heart. The inhibition is promoted by an abortive binary complex formed by the enzymes and the enol form of of oxalacelate. Neither the oxidized coenzyme nor the reduced coenzyme appears to be involved in the formation of this complex. These results suggest that the mechanism of substrate inhibition that occurs with the pig heart malate dehydrogenases is different from that observed with the lactate dehydrogenases from chicken hearts. The inhibition constants for oxalacetate are 2.0 mM with the mitochondrial enzyme and 4.5 mM with the cytoplasmic enzyme. Since the in vivo concentration of oxalacetate is reported to be about 10 micrometer, these data suggest that the substrate inhibition that is exhibited by the malate dehydrogenases may not be of any significance in vivo.