title: Reaction of cytochrome c in the electron-transport chain of Paracoccus denitrificans.
abstract: The reaction of the cytochrome c oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) of Paracoccus denitrificans cytoplasmic membranes with the endogenous cytochrome c of the membranes was studied, as well as its interaction with added exogenous cytochrome c from P. denitrificans or bovine heart. The polarographic method was employed, using N,N,N',N'-tetramethyl-p-phenylenediamine plus ascorbate to reduce the cytochrome c. We found that overall electron transport can proceed maximally while the cytochrome c remains membrane bound; NADH or succinoxidase activities were not inhibited by the addition of substances which bind the P. denitrificans cytochrome c strongly. In contrast to our observations with the spectrophotometric method (Smith, L., Davies, H.C. and Nava, M.E. (1976) Biochemistry 15, 5827-5831), in the polarographic assays the membrane-bound oxidase reacts with about equal rapidity with exogenous bovine and P. denitrificans cytochromes c. The reaction of the oxidase with the endogenous cytochrome c proceeds at high rates and preferentially to that with exogenous cytochrome c; the reaction with the latter, but not the former is inhibited by positively charged poly(L-lysine). The cytochrome c and the oxidase appear to be very closely associated on the membrane.
mesh_terms: D000818:Animals; D002417:Cattle; D003574:Cytochrome c Group / Q000378:metabolism*; D003840:Deoxycholic Acid / Q000494:pharmacology; D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000378:metabolism; D009097:Multienzyme Complexes / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism; D010231:Paracoccus denitrificans / Q000201:enzymology*; D013772:Tetramethylphenylenediamine / Q000494:pharmacology
chemical_list: D003574:Cytochrome c Group; D009097:Multienzyme Complexes; D003840:Deoxycholic Acid; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D003576:Electron Transport Complex IV; D013772:Tetramethylphenylenediamine; D010100:Oxygen