title: Participation of cytochromes in some oxidation-reduction systems in Campylobacter fetus.
abstract: Campylobacter species are rich in c-type cytochromes, including forms which bind carbon monoxide. The role of the various forms of cytochromes in Campylobacter fetus has been examined in cell-free preparations by using physiological electron donor and acceptor systems. Under anaerobic conditions, NADPH reduced essentially all of the cytochrome c in crude cell extracts, whereas the reduction level with succinate was 50 to 60%. The carbon monoxide spectrum with NADPH was predominated by the cytochrome c complex; evidence of a cytochrome o type was seen in the succinate-reduced extracts and in membrane fractions. Succinate-reduced cytochrome c was oxidized by oxygen via a cyanide-sensitive, membrane-associated system. NADPH-reduced cytochrome c was oxidized by a cyanide-insensitive system. Partially purified carbon monoxide-binding cytochrome c, isolated from the cytoplasm, could serve as electron acceptor for NADPH-cytochrome c oxidoreductase; the reduced cytochrome was oxidized by oxygen by a cyanide-insensitive system present in the cytoplasmic fraction. Horse heart cytochrome c was also reducible by NADPH and by succinate; the reduced cytochrome was oxidized by a cyanide-sensitive system in the membrane fraction. NADPH and NADH oxidase activities were observed aerobically and under anaerobic conditions with fumarate. NADPH was more active than NADH. NADP was also more effective than NAD as an electron acceptor for the coenzyme A-dependent pyruvate and alpha-ketoglutarate dehydrogenase activities found in crude extracts. These dehydrogenases used methyl viologen and metronidazole as electron acceptors; they could be loci for oxygen inhibition of growth. It is proposed that energy provision via the high-potential cytochrome c oxidase system in the cytoplasmic membrane is limited by oxygen-sensitive primary dehydrogenases and that the carbon monoxide-binding cytochrome c may have a role as an oxygen scavenger.
mesh_terms: D002168:Campylobacter fetus / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology; D002952:Citric Acid Cycle; D003574:Cytochrome c Group / Q000378:metabolism; D003580:Cytochromes / Q000502:physiology*; D003593:Cytoplasm / Q000201:enzymology; D007655:Ketoglutarate Dehydrogenase Complex / Q000032:analysis; D009097:Multienzyme Complexes / Q000032:analysis; D009247:NADH, NADPH Oxidoreductases / Q000032:analysis; D009249:NADP / Q000378:metabolism; D019255:NADPH Oxidases; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D011768:Pyruvate Dehydrogenase Complex / Q000032:analysis; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid
chemical_list: D003574:Cytochrome c Group; D003580:Cytochromes; D009097:Multienzyme Complexes; D011768:Pyruvate Dehydrogenase Complex; D013386:Succinates; D009249:NADP; D019802:Succinic Acid; D007655:Ketoglutarate Dehydrogenase Complex; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D010100:Oxygen