title: Characterization of the respiratory chain of Helicobacter pylori.
abstract: The respiratory chain of Helicobacter pylori has been investigated. The total insensitivity of activities of NADH dehydrogenase to rotenone and of NADH-cytochrome c reductase to antimycin is indicative of the absence of the classical complex I of the electron transfer chain in this bacterium. NADPH-dependent respiration was significantly stronger than NADH-dependent respiration, indicating that this is a major respiratory electron donor in H. pylori. Fumarate and malonate exhibited a concentration-dependent inhibitory effect on the activity of succinate dehydrogenase. The activity of succinate-cytochrome c reductase was inhibited by antimycin, implying the presence of a classical pathway from complex II to complex III in this bacterium. The presence of NADH-fumarate reductase (FRD) was demonstrated in H. pylori and fumarate could reduce H2O2 production from NADH, indicating fumarate to be an endogenous substrate for accepting electrons from NADH. The activity of NADH-FRD was inhibited by 2-thenoyltrifluoroacetone. A tentative scheme for the electron transfer pathway in H. pylori is proposed, which may be helpful in clarifying the pathogenesis of H. pylori and in opening new lines for chemotherapy against this bacterium.
authors.affiliation: Department of Clinical Microbiology, University Hospital (Rigshospitalet), Copenhagen, Denmark. cmcmp@rh.dk
authors.forename: M
authors.initials: M
authors.lastname: Chen
authors.forename: L P
authors.initials: LP
authors.lastname: Andersen
authors.forename: L
authors.initials: L
authors.lastname: Zhai
authors.forename: A
authors.initials: A
authors.lastname: Kharazmi
mesh_terms: D004579:Electron Transport; D005650:Fumarates / Q000378:metabolism; D016481:Helicobacter Infections / Q000382:microbiology; D016480:Helicobacter pylori / Q000201:enzymology / Q000378:metabolism*; D006801:Humans; D009245:NADH Dehydrogenase; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D013384:Succinate Cytochrome c Oxidoreductase; D013385:Succinate Dehydrogenase; D019802:Succinic Acid / Q000378:metabolism / Q000494:pharmacology; D013804:Thenoyltrifluoroacetone / Q000378:metabolism / Q000494:pharmacology
chemical_list: D005650:Fumarates; D013804:Thenoyltrifluoroacetone; C032005:fumaric acid; D019802:Succinic Acid; D013384:Succinate Cytochrome c Oxidoreductase; D013385:Succinate Dehydrogenase; D009245:NADH Dehydrogenase