title: Effect of O2, H2 and redox potential on the activity and synthesis of hydrogenase 2 in Escherichia coli.
abstract: The aim of this work was to study the influence of O2 with special emphasis on low oxygen tension, the effect of H2 under various conditions of oxygen tension and the influence of the redox potential in the growth medium on hydrogenase 2 of Escherichia coli. The hydrogenase activity and the content of the large (HybC) and small (HybO) subunits of hydrogenase 2 were compared during turbidostat cultivation in a wild strain and mutant HDK103 lacking hydrogenases 1 and 3. No hydrogenase 2 activity in the mutant HDK103 was observed under aerobic conditions, but it was maximal under anaerobic conditions and half-maximal at an oxygen tension of approximately 4 mbar as is common for enzymes of anaerobic respiration. The content of hydrogenase 2 in both the strains was maximal under anaerobic conditions. In the wild strain, H2 addition enhanced hydrogenase activity and the HybO content under microaerobic conditions only. Under anaerobic conditions endogenous H2 production hindered this effect. Under aerobic conditions, the 02-related negative effect seemed to dominate over the H2-related positive effect. By contrast, in the mutant HDK103, hydrogen influenced neither hydrogenase 2 activity nor its content. A possible role of hydrogenase I in the response of hydrogenase 2 to hydrogen is discussed. Under conditions of different O2 tension, hydrogenase activity in both strains correlated inversely with the value of the redox potential of the medium. The presence of H2 changed this dependence. Thus, the value of the redox potential itself is not a controlling factor for hydrogenase 2.
authors.affiliation: Laboratory of Biotechnology and Physiology of Phototrophic Organisms, Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region.
authors.forename: T V
authors.initials: TV
authors.lastname: Laurinavichene
authors.forename: A
authors.initials: A
authors.lastname: Chanal
authors.forename: L F
authors.initials: LF
authors.lastname: Wu
authors.forename: A A
authors.initials: AA
authors.lastname: Tsygankov
mesh_terms: D000332:Aerobiosis; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D006859:Hydrogen / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000235:genetics / Q000378:metabolism*; D010100:Oxygen / Q000494:pharmacology*
chemical_list: D006859:Hydrogen; D010088:Oxidoreductases; C029746:uptake hydrogenase; D010100:Oxygen