Characterization of the respiratory chain of Helicobacter pylori

The respiratory chain of Helicobacter. pylori has been investigated. The to tal insensitivity of activities of NADH dehydrogenase to rotenone and of NA DH-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 respi ration, indicating that this is a major respiratory electron donor in H. py lori. Fumarate and malonate exhibited a concentration-dependent inhibitory effect on the activity of succinate dehydrogenase. The activity of succinat e-cytochrome c reductase was inhibited by antimycin, implying the presence of a classical pathway from complex II to complex III in this bacterium. Th e presence of NADH-fumarate reductase (FRD) was demonstrated in H, pylori a nd 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 he lpful in clarifying the pathogenesis of H. pylori and in opening new lines for chemotherapy against this bacterium. (C) 1999 Federation of European Mi crobiological Societies. Published by Elsevier Science B.V, All rights rese rved.