Dihydroorotate-ubiquinone oxidoreductase links mitochondria in the biosynthesis of pyrimidine nucleotides
Dihydroorotate-ubiquinone oxidoreductase links mitochondria in the biosynthesis of pyrimidine nucleotides
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DOI：
10.1023/a:1006859115450
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发表时间：
1997-09-01
影响因子：
4.3
通讯作者：
Becker, C
中科院分区：
文献类型：
--
作者：
Loffler, M;Jockel, J;Becker, C
嘧啶和嘌呤(脱氧)核苷酸是DNA和RNA的组成成分。核苷二磷酸糖，如UDP-葡萄糖，是糖之间几乎所有糖苷键合成的活性中间体。在哺乳动物中，对嘧啶的需求是通过UMP从头合成来满足的，在一定程度上，通过挽救游离核苷来满足。线粒体结合的二氢罗酸脱氢酶(‘DHOdehase’或‘DHODH’，EC 1.3.99.11)的从头合成的异常区隔是本工作的重点之一。DHODH活性由二氢轮酸依赖的耗氧量或产物与啮齿动物和猪组织线粒体的紫外光吸收来确定。为了进行比较，测量了不同组织线粒体的细胞色素c和胆碱依赖的氧耗量。大鼠DHODH的比活力最高的是肝脏(2.3×10~(-3)pmol/min×mg蛋白)、肾脏和心脏。已知的酶抑制剂来氟米特和来氟米特用于DHODH，氰化钠用于细胞色素C氧化酶，验证了所用活性测试的特异性。DHODH活性与细胞色素c氧化酶活性的关系显示，心肌线粒体中DHODH活性最低，肝脏线粒体中DHODH活性最高。由于线粒体能量代谢障碍可能导致呼吸链偶联脱氢酶(DHODH)对嘧啶生物合成的严重损害，因此建议在治疗方案中包括改善嘧啶核苷酸状态。
Pyrimidines and purine (deoxy)nucleotides are the building blocks of DNA and RNA. Nucleoside diphosphate sugars, e.g. UDP-glucose, are the reactive intermediates in the synthesis of nearly all glycosidic bonds between sugars.In mammals the requirement for pyrimidines is met by UMP de novo synthesis and, to a greater or lesser extent, by salvage of free nucleosides. The exceptional compartmentation of the de novo synthesis with respect to mitochondrially-bound dihydroorotate dehydrogenase ('DHOdehase' or 'DHODH', EC 1.3.99.11) is one focus of the present work. DHODH activity was determined by the dihydroorotate-dependent oxygen consumption or by the UV absorption of the product orotate with mitochondria isolated from rodent and porcine tissues. For comparison, the cytochrome c and choline-dependent oxygen consumption of mitochondria from different tissues was measured. The highest specific activity of the rat DHODH was found in liver (2.3 x 10(-3) pmol/min x mg protein) > kidney > heart. The application of known enzyme inhibitors Brequinar Sodium and Leflunomide for DHODH and sodium cyanide for cytochrome c oxidase verified the specificity of the activity tests used. The relation of DHODH activity versus that of cytochrome c oxidase revealed the lowest ratios in heart mitochondria and the highest in liver mitochondria. Since disorders in the mitochondrial energy metabolism could entail severe impairment of pyrimidine biosynthesis via respiratory-chain coupled DHODH, it is suggested to include improvement of pyrimidine nucleotide status in therapy protocols.