title: Monovalent nickel in hydrogenase from Chromatium vinosum. Light sensitivity and evidence for direct interaction with hydrogen.
abstract: Redox titrations with hydrogenase from Chromatium vinosum show that its nickel ion can exist in 3, possibly 4, different redox states: the 3+, 2+, 1+ and possibly a zero valent state. The 1+ state is unstable: oxidation to Ni(II) occurs unless H2 gas is present. The Ni(I) coordination, but not that of Ni(III), is highly light sensitive. A photoreaction occurs on illumination. It is irreversible below 77 K, but reversible at 200 K. The rate of this photodissociation reaction in 2H2O is nearly 6-times slower than in H2O, indicating the breakage of a nickel-hydrogen bond. This forms the first evidence for an H atom in the direct coordination sphere of Ni in hydrogenase and for the involvement of this metal in the reaction with hydrogen.
authors.forename: J W
authors.initials: JW
authors.lastname: van der Zwaan
authors.forename: S P
authors.initials: SP
authors.lastname: Albracht
authors.forename: R D
authors.initials: RD
authors.lastname: Fontijn
authors.forename: E C
authors.initials: EC
authors.lastname: Slater
mesh_terms: D002844:Chromatium / Q000201:enzymology*; D003903:Deuterium; D004578:Electron Spin Resonance Spectroscopy; D006859:Hydrogen; D006860:Hydrogen Bonding; D006864:Hydrogenase / Q000528:radiation effects; D008027:Light; D009532:Nickel / Q000528:radiation effects*; D010084:Oxidation-Reduction
chemical_list: D009532:Nickel; D006859:Hydrogen; D003903:Deuterium; D006864:Hydrogenase