ANALYSIS OF THE KINETIC MECHANISM OF THE BOVINE LIVER MITOCHONDRIAL DIHYDROOROTATE DEHYDROGENASE
ANALYSIS OF THE KINETIC MECHANISM OF THE BOVINE LIVER MITOCHONDRIAL DIHYDROOROTATE DEHYDROGENASE
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DOI：
10.1021/bi00429a040
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发表时间：
1989-02-07
期刊：
影响因子：
2.9
通讯作者：
JOHNSTON, M
中科院分区：
文献类型：
--
作者：
HINES, V;JOHNSTON, M
研究了高纯度牛肝脏线粒体二氢羟酸脱氢酶的稳态动力学机制。用s -二氢旋酸酯和辅酶Q6进行初始速度分析，发现了类似平行的双倒易图，表明了乒乓机制。与巴比妥酸的死端抑制模式以及与交替的辅酶底物甲基- s -二氢乙酸和甲萘醌的反应也指向乒乓机制。然而，产物旋酸酯被发现与二氢旋酸酯竞争，而与Q6无竞争。这些发现表明，二氢乙酸脱氢酶可能遵循一种非经典的、两个位点的乒乓机制，这种机制是一种典型的酶，它包含两个不重叠的、动力学分离的底物结合位点。酶的动力学行为也表明，这两个位点通过涉及FMN和铁硫中心的分子内电子转移系统进行通信。
The steady-state kinetic mechanism of highly purified bovine liver mitochondrial dihydroorotate dehydrogenase has been investigated. Initial velocity analysis using S-dihydroorotate and coenzyme Q6 revealed parallel-like, double-reciprocal plots, indicative of a ping-pong mechanism. The dead-end inhibition pattern with barbituric acid and the reactions with alternate cosubstrates methyl-S-dihydroorotate and menadione also point to a ping-pong mechanism. However, product orotate was found to be competitive with dihydroorotate and uncompetitive with Q6. These findings suggest that dihydroorotate dehydrogenase may follow a nonclassical, two-site ping-pong mechanism, typical of an enzyme that contains two nonoverlapping and kinetically isolated substrate binding sites. That these two sites communicate by an intramolecular electron-transfer system involving FMN and perhaps an iron-sulfur center is also suggested by the kinetic behavior of the enzyme.