Hillar A, Nicholls P
Department of Biological Sciences, Brock University, St. Catharines, Ontario, Canada.
FEBS Lett. 1992 Dec 14;314(2):179-82. doi: 10.1016/0014-5793(92)80969-n.
Catalase-bound NADPH both prevents and reverses the accumulation of inactive bovine liver catalase peroxide compound II generated by 'endogenous' donors under conditions of steady H2O2 formation without reacting rapidly with either compound I or compound II. It thus differs both from classical 2-electron donors of the ethanol type, and from 1-electron donors of the ferrocyanide/phenol type. NADPH also inhibits compound II formation induced by the exogenous one-electron donor ferrocyanide. A catalase reaction scheme is proposed in which the initial formation of compound II from compound I involves production of a neighbouring radical species. NADPH blocks the final formation of stable compound II by reacting as a 2-electron donor to compound II and to this free radical. The proposed behaviour resembles that of labile free radicals formed in cytochrome c peroxidase and myoglobin. Such radical migration patterns within haem enzymes are increasingly common motifs.
与过氧化氢酶结合的烟酰胺腺嘌呤二核苷酸磷酸（NADPH）既能防止又能逆转在稳定生成过氧化氢的条件下由“内源性”供体产生的无活性牛肝过氧化氢酶过氧化物化合物II的积累，且不会与化合物I或化合物II快速反应。因此，它既不同于乙醇类型的经典双电子供体，也不同于亚铁氰化物/苯酚类型的单电子供体。NADPH还能抑制由外源性单电子供体亚铁氰化物诱导的化合物II的形成。提出了一种过氧化氢酶反应方案，其中从化合物I开始形成化合物II涉及产生相邻的自由基物种。NADPH通过作为双电子供体与化合物II和这种自由基反应，阻止稳定化合物II的最终形成。所提出的行为类似于细胞色素c过氧化物酶和肌红蛋白中形成的不稳定自由基的行为。这种血红素酶内的自由基迁移模式是越来越常见的基序。
