title: Effect of redox potential on activity of hydrogenase 1 and hydrogenase 2 in Escherichia coli.
abstract: This report elucidates the distinctions of redox properties between two uptake hydrogenases in Escherichia coli. Hydrogen uptake in the presence of mediators with different redox potential was studied in cell-free extracts of E. coli mutants HDK103 and HDK203 synthesizing hydrogenase 2 or hydrogenase 1, respectively. Both hydrogenases mediated H(2) uptake in the presence of high-potential acceptors (ferricyanide and phenazine methosulfate). H(2) uptake in the presence of low-potential acceptors (methyl and benzyl viologen) was mediated mainly by hydrogenase 2. To explore the dependence of hydrogen consumption on redox potential of media in cell-free extracts, a chamber with hydrogen and redox ( E(h)) electrodes was used. The mutants HDK103 and HDK203 exhibited significant distinctions in their redox behavior. During the redox titration, maximal hydrogenase 2 activity was observed at the E(h) below -80 mV. Hydrogenase 1 had maximum activity in the E(h) range from +30 mV to +110 mV. Unlike hydrogenase 2, the activated hydrogenase 1 retained activity after a fast shift of redox potential up to +500 mV by ferricyanide titration and was more tolerant to O(2). Thus, two hydrogenases in E. coli are complementary in their redox properties, hydrogenase 1 functioning at higher redox potentials and/or at higher O(2) concentrations than hydrogenase 2.
authors.affiliation: Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow region, 142290 Russia.
authors.forename: Tatyana V
authors.initials: TV
authors.lastname: Laurinavichene
authors.forename: Nikolai A
authors.initials: NA
authors.lastname: Zorin
authors.forename: Anatoly A
authors.initials: AA
authors.lastname: Tsygankov
mesh_terms: D004579:Electron Transport; D004789:Enzyme Activation; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D006859:Hydrogen / Q000494:pharmacology; D006864:Hydrogenase / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism; D010100:Oxygen / Q000494:pharmacology*
chemical_list: D006859:Hydrogen; D010088:Oxidoreductases; C029746:uptake hydrogenase; D006864:Hydrogenase; D010100:Oxygen