MENADIONE-(2-METHYL-1,4-NAPHTHOQUINONE) DEPENDENT ENZYMATIC REDOX CYCLING AND CALCIUM RELEASE BY MITOCHONDRIA
MENADIONE-(2-METHYL-1,4-NAPHTHOQUINONE) DEPENDENT ENZYMATIC REDOX CYCLING AND CALCIUM RELEASE BY MITOCHONDRIA
复制标题
DOI：
10.1021/bi00363a040
复制
发表时间：
1986-07-29
期刊：
影响因子：
2.9
通讯作者：
RICHTER, C
中科院分区：
文献类型：
--
作者：
FREI, B;WINTERHALTER, KH;RICHTER, C
结果表明，线粒体中存在三种不同的甲萘醌（2-甲基-1,4-萘醌）还原酶：NAD(P)H:（醌受体）氧化还原酶（D,T-diaphorase）、NADPH:（醌受体）氧化还原酶和NADH:（醌受体）氧化还原酶。这三种酶在双电子步骤中将甲萘醌直接还原为对苯二酚。NADH-泛醌氧化还原酶（NADH脱氢酶）和NAD(P)H偶氮还原酶不参与甲萘醌还原。在线粒体提取物中，甲萘醌诱导的NAD(P)H氧化发生在醌的化学计量还原之外，并伴随着氧气消耗。苯醌的还原速度比甲萘酮快，但不经历氧化还原循环。在完整的线粒体中，甲萘醌触发线粒体内吡啶核苷酸的氧化，对氰化物不敏感的氧消耗，以及瞬时的delta…psi的降低。在线粒体内Ca2+存在的情况下，甲萘醌诱导的吡啶核苷酸氧化伴随着它们的水解，Ca2+从线粒体中释放出来。甲萘醌诱导的Ca2+释放使线粒体完整，提供过量的Ca2+循环被阻止。在硒缺乏和硒充足的线粒体中，甲萘醌在诱导吡啶核苷酸氧化和Ca2+释放方面同样有效。因此，menadione诱导的Ca2+释放主要是通过menadione的酶促双电子还原介导的，而不是通过menadione依赖的氧化还原循环产生的H2O2。我们的研究结果反对D， t -二磷酸腺苷酶是防止线粒体中醌依赖性氧毒性的控制装置。
The results presented in this paper reveal the existence of three distinct menadione (2-methyl-1,4-naphthoquinone) reductases in mitochondria: NAD(P)H:(quinone-acceptor) oxidoreductase (D,T-diaphorase), NADPH:(quinone-acceptor) oxidoreductase, and NADH:(quinone-acceptor) oxidoreductase. All three enzymes reduce menadione in a two-electron step directly to the hydroquinone form. NADH-ubiquinone oxidoreductase (NADH dehydrogenase) and NAD(P)H azoreductase do not participate significantly in menadione reduction. In mitochondrial extracts, the menadione-induced NAD(P)H oxidation occurs beyond stoichiometric reduction of the quinone and is accompanied by O2 consumption. Benzoquinone is reduced more rapidly than menadione but does not undergo redox cycling. In intact mitochondria, menadione triggers oxidation of intramitochondrial pyridine nucleotides, cyanide-insensitive O2 consumption, and a transient decrease of .DELTA..psi.. In the presence of intramitochondrial Ca2+, the menadione-induced oxidation of pyridine nucleotides is accompanied by their hydrolysis, and Ca2+ is released from mitochondria. The menadione-induced Ca2+ release leaves mitochondria intact, provided excessive Ca2+ cycling is prevented. In both selenium-deficient and selenium-adequate mitochondria, menadione is equally effective in inducing oxidation of pyridine nucleotides and Ca2+ release. Thus, menadione-induced Ca2+ release is mediated predominantly by enzymatic two-electron reduction of menadione, and not by H2O2 generated by menadione-dependent redox cycling. Our findings argue against D,T-diaphorase being a control device that prevents quinone-dependent oxygen toxicity in mitochondria.