title: Purification and properties of the H2-oxidizing (uptake) hydrogenase of the N2-fixing anaerobe Clostridium pasteurianum W5.
abstract: Clostridium pasteurianum has two distinct hydrogenases, the bidirectional hydrogenase and the H2-oxidizing (uptake) hydrogenase. The H2-oxidizing hydrogenase has been purified (up to 970-fold) to a specific activity of 17,600 mumol H2 oxidized/min X mg protein (5 mM methylene blue) or 3.5 mumol H2 produced/min X mg protein (1 mM methyl viologen). The uptake hydrogenase has a Mr of 53,000 (one polypeptide chain). Depending upon how protein was measured, the Fe and S = contents (gatom/mol) were 4.7 and 5.2 (by the dye-binding assay) or 7.2 and 8.0 (by the Lowry method). Both reduced and oxidized forms of the enzyme gave electron paramagnetic resonance signals. The activation energy for H2-production and H2-oxidation by the uptake hydrogenase was 59.1 and 31.2 kJ/mol, respectively. In the exponential phase of growth, the ratio of uptake hydrogenase/bidirectional hydrogenase in NH3-grown cells was much lower than that in N2-fixing cells.
mesh_terms: D000693:Anaerobiosis; D055598:Chemical Phenomena; D002621:Chemistry; D002848:Chromatography, DEAE-Cellulose; D003013:Clostridium / Q000201:enzymology* / Q000254:growth & development; D004578:Electron Spin Resonance Spectroscopy; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006864:Hydrogenase; D009586:Nitrogen Fixation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D013696:Temperature
chemical_list: D006859:Hydrogen; D010088:Oxidoreductases; D006864:Hydrogenase