Kurosawa K, Shibata H, Hayashi N, Sato N, Kamada T, Tagawa K
Department of Physiological Chemistry, Osaka University Medical School.
J Biochem. 1990 Jul;108(1):9-16. doi: 10.1093/oxfordjournals.jbchem.a123169.
Hydroperoxide decomposition by the NADP-glutathione system in rat liver mitochondria was analyzed. Mitochondria were found to contain high concentrations of the reduced form of glutathione (GSH) (4.32 +/- 0.50 nmol/mg) and NADPH (4.74 +/- 0.64 nmol/mg), and high activities of glutathione peroxidase and reductase. In the initial phase of the reaction, the rate of hydroperoxide decomposition was proportional to both the GSH level and the activity of GSH peroxidase. However, in the later steady state, the step of NADP reduction was rate-limiting, and the overall reaction rate was independent of the initial concentration of GSH, and activities of glutathione peroxidase and reductase. Some GSH was released from mitochondria during incubation, but the rate of the decomposition could be simply expressed as kappa [GSH]/2, where kappa is the first-order rate constant of the peroxidase and [GSH] is the intramitochondrial level of GSH in the steady state. The rate of the reaction in the steady state was also dependent on the NADPH level, its reciprocal being linearly correlated with [NADPH]-1. The rate of decomposition of hydroperoxide was influenced by the respiratory state. During state 3 respiration, the rate was greatly depressed, but was still considered to exceed by far the rate of physiological generation of hydroperoxide.
对大鼠肝脏线粒体中烟酰胺腺嘌呤二核苷酸磷酸（NADP）-谷胱甘肽系统催化的过氧化氢分解进行了分析。发现线粒体含有高浓度的还原型谷胱甘肽（GSH）（4.32±0.50 nmol/mg）和烟酰胺腺嘌呤二核苷酸磷酸（NADPH）（4.74±0.64 nmol/mg），以及高活性的谷胱甘肽过氧化物酶和还原酶。在反应的初始阶段，过氧化氢分解速率与GSH水平和谷胱甘肽过氧化物酶活性均成正比。然而，在后期稳态阶段，NADP还原步骤是限速步骤，总反应速率与GSH的初始浓度、谷胱甘肽过氧化物酶和还原酶的活性无关。孵育过程中有一些GSH从线粒体中释放出来，但分解速率可以简单地表示为κ[GSH]/2，其中κ是过氧化物酶的一级速率常数，[GSH]是稳态时线粒体内GSH的水平。稳态反应速率也取决于NADPH水平，其倒数与[NADPH]-1呈线性相关。过氧化氢的分解速率受呼吸状态的影响。在状态3呼吸期间，速率大大降低，但仍被认为远远超过过氧化氢的生理生成速率。
