title: Reversible active site sulfoxygenation can explain the oxygen tolerance of a NAD+-reducing [NiFe] hydrogenase and its unusual infrared spectroscopic properties.
abstract: Oxygen-tolerant [NiFe] hydrogenases are metalloenzymes that represent valuable model systems for sustainable H2 oxidation and production. The soluble NAD(+)-reducing [NiFe] hydrogenase (SH) from Ralstonia eutropha couples the reversible cleavage of H2 with the reduction of NAD(+) and displays a unique O2 tolerance. Here we performed IR spectroscopic investigations on purified SH in various redox states in combination with density functional theory to provide structural insights into the catalytic [NiFe] center. These studies revealed a standard-like coordination of the active site with diatomic CO and cyanide ligands. The long-lasting discrepancy between spectroscopic data obtained in vitro and in vivo could be solved on the basis of reversible cysteine oxygenation in the fully oxidized state of the [NiFe] site. The data are consistent with a model in which the SH detoxifies O2 catalytically by means of an NADH-dependent (per)oxidase reaction involving the intermediary formation of stable cysteine sulfenates. The occurrence of two catalytic activities, hydrogen conversion and oxygen reduction, at the same cofactor may inspire the design of novel biomimetic catalysts performing H2-conversion even in the presence of O2.
authors: Institut für Chemie, Technische Universität Berlin , Sekr. PC14, Straße des 17, Juni 135, D-10623 Berlin, Germany.
authors: Marius
authors: M
authors: Horch
authors: Lars
authors: L
authors: Lauterbach
authors: Maria Andrea
authors: MA
authors: Mroginski
authors: Peter
authors: P
authors: Hildebrandt
authors: Oliver
authors: O
authors: Lenz
authors: Ingo
authors: I
authors: Zebger
mesh_terms: D020134:Catalytic Domain; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism*; D009243:NAD / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D012995:Solubility; D013055:Spectrophotometry, Infrared
chemical_list: D009243:NAD; C043296:nickel-iron hydrogenase; D006864:Hydrogenase; D010100:Oxygen