title: Nickel in the catalytically active hydrogenase of Alcaligenes eutrophus.
abstract: Nickel is a constituent of soluble and particulate hydrogenase of Alcaligenes eutrophus. Incorporation of 63Ni2+ revealed that almost the total nickel taken up by the cells was bound to the protein. Chromatography of a crude extract on diethylaminoethyl cellulose demonstrated an association of 63Ni2+ with soluble and particulate hydrogenase, supported by further analysis like polyacrylamide gel electrophoresis. Unspecific binding of 63Ni2+ to the protein was excluded by comparison with a mutant extract free of hydrogenase protein. X-ray fluorescence analysis of the homogeneous soluble hydrogenase indicated the presence of 2 mol of nickel per mol of enzyme, whereas the amount of nickel determined by incorporation of 63Ni2+ was calculated to be approximately 1 mol/mol of enzyme. Cells grown under nickel limitation contained catalytically inactive, but serologically active, soluble and particulate hydrogenase. The immunochemical reactions were only partially identical with the enzyme from nickel-cultivated cells indicating a structural modification of the proteins in the absence of nickel. It is concluded that nickel is essential for the catalytic activity of hydrogenase and not involved as a regulatory component in the synthesis of this enzyme.
mesh_terms: D000421:Alcaligenes / Q000201:enzymology*; D006864:Hydrogenase; D008566:Membranes / Q000201:enzymology; D009532:Nickel / Q000032:analysis* / Q000378:metabolism; D010088:Oxidoreductases / Q000032:analysis* / Q000302:isolation & purification / Q000378:metabolism
chemical_list: D009532:Nickel; D010088:Oxidoreductases; D006864:Hydrogenase