Villalba J M, Navarro F, Córdoba F, Serrano A, Arroyo A, Crane F L, Navas P
Departamento de Biología Celular, Facultad de Ciencias, Universidad de Cordoba, Spain.
Proc Natl Acad Sci U S A. 1995 May 23;92(11):4887-91. doi: 10.1073/pnas.92.11.4887.
A specific requirement for coenzyme Q in the maintenance of trans-plasma-membrane redox activity is demonstrated. Extraction of coenzyme Q from membranes resulted in inhibition of NADH-ascorbate free radical reductase (trans electron transport), and addition of coenzyme Q10 restored the activity. NADH-cytochrome c oxidoreductase (cis electron transport) did not respond to the coenzyme Q status. Quinone analogs inhibited trans-plasma-membrane redox activity, and the inhibition was reversed by coenzyme Q. A 34-kDa coenzyme Q reductase (p34) has been purified from pig-liver plasma membranes. The isolated enzyme was sensitive to quinone-site inhibitors. p34 catalyzed the NADH-dependent reduction of coenzyme Q10 after reconstitution in phospholipid liposomes. When plasma membranes were supplemented with extra p34, NADH-ascorbate free radical reductase was activated but NADH-cytochrome c oxidoreductase was not. These results support the involvement of p34 as a source of electrons for the trans-plasma-membrane redox system oxidizing NADH and support coenzyme Q as an intermediate electron carrier between NADH and the external acceptor ascorbate free radical.
已证实辅酶Q在维持跨质膜氧化还原活性方面有特定需求。从膜中提取辅酶Q会导致NADH - 抗坏血酸自由基还原酶（跨膜电子传递）受到抑制，而添加辅酶Q10可恢复该活性。NADH - 细胞色素c氧化还原酶（顺式电子传递）对辅酶Q状态无反应。醌类似物会抑制跨质膜氧化还原活性，且这种抑制可被辅酶Q逆转。已从猪肝质膜中纯化出一种34 kDa的辅酶Q还原酶（p34）。分离出的酶对醌位点抑制剂敏感。p34在重新组装到磷脂脂质体后催化依赖NADH的辅酶Q10还原反应。当向质膜中补充额外的p34时，NADH - 抗坏血酸自由基还原酶被激活，但NADH - 细胞色素c氧化还原酶未被激活。这些结果支持p34作为跨质膜氧化还原系统中氧化NADH的电子来源的参与，并支持辅酶Q作为NADH与外部受体抗坏血酸自由基之间的中间电子载体。
