title: Coenzyme Q reductase from liver plasma membrane: purification and role in trans-plasma-membrane electron transport.
abstract: 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.
authors.affiliation: Departamento de Biología Celular, Facultad de Ciencias, Universidad de Cordoba, Spain.
authors.forename: J M
authors.initials: JM
authors.lastname: Villalba
authors.forename: F
authors.initials: F
authors.lastname: Navarro
authors.forename: F
authors.initials: F
authors.lastname: Córdoba
authors.forename: A
authors.initials: A
authors.lastname: Serrano
authors.forename: A
authors.initials: A
authors.lastname: Arroyo
authors.forename: F L
authors.initials: FL
authors.lastname: Crane
authors.forename: P
authors.initials: P
authors.lastname: Navas
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D042967:Electron Transport Complex I; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008854:Microscopy, Electron; D008970:Molecular Weight; D009247:NADH, NADPH Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism*; D013379:Substrate Specificity; D013552:Swine
chemical_list: D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I