Electron transport reactions in respiratory particles of hydrogenase-induced Anacystis nidulans

Respiratory particles from hydrogen-grown Anacystis nidulans were found to oxidize H₂, NADPH, NADH, succinate and ascorbate plus N,N,N,N-tetramethyl-p-phenylenediamine at rates corresponding to 28, 15, 6, 2.5, and 70 nmol O₂ taken up x mg protein^–1xmin^–1, respectively. The particles were isolated by brief sonication of lysozyme-pretreated cells. Respiratory activities were studied in terms of both substrate oxidation and O₂ uptake. The stoichiometry between oxidation of H₂, NADPH, NADH or succinate, and consumption of O₂ was calculated to be 1.95+-0.1 with each substrate.Inhibitors of flavoproteins did not affect the oxyhydrogen reaction while 2-n-heptyl-8-hydroxyquinoline-N-oxide as well as compounds known to block the terminal oxidase impaired the oxidation of both H₂ and of NAD(P)H or succinate in a parallel fashion. No additivity of O₂ uptake was observed when NADPH, NADH or succinate was present in addition to H₂. Instead, H₂ uptake was depressed under such conditions, and also the oxidation of NAD(P)H or succinate was increasingly lowered by increasing H₂ tensions.The results suggest that in Anacystis molecular hydrogen is oxidized through the same type of respiratory chain as are NAD(P)H and succinate. Moreover, the cyanide-resistant branch of respiratory O₂ uptake will be discussed, and a few results obtained with particles prepared from thylakoid-free Anacystis will also be presented.Abbreviations BAL 2,3-dimercaptopropanol-(1) - DCPIP 2,6-dichlorophenolindophenol - HOQNO 2-n-heptyl-8-hydroxyquinoline-N-oxide - TMPD N,N,N,N-tetramethyl-p-phenylenediamine - tricine N-tris-(hydroxymethyl)-methylglycine - Tris tris-(hydroxymethyl)-aminomethane - TTFA thenoyltrifluoroacetoneNAD(P)H indicates NADPH and/or NADH