1.12.1.2 CN- - 706499 1.12.1.2 CN- enzyme contains four cyanides in its active site, one is bound to the Ni2+, the active site is a (enzyme-Cys)2(CN)Ni(micro-enzyme-Cys)2Fe(CN)3(CO) centre, the CN- bound to the nickel ion can be irreversibly removed inducing enzyme inhibition by oxygen 655890 1.12.1.2 CN- enzyme contains four cyanides in its active site, the Ni2+ bound one is responsible for the insensitivity towards oxygen, the active site is a (enzyme-Cys)2(CN)Ni(micro-enzyme-Cys)2Fe(CN)3(CO) centre, the CN- bound to the nickel ion can be irreversibly removed inducing enzyme inhibition by oxygen 654562, 656298 1.12.1.2 CO - 706499 1.12.1.2 CO bound to the active site, the active site is a (enzyme-Cys)2(CN)Ni(micro-enzyme-Cys)2Fe(CN)3(CO) centre 654562, 656298 1.12.1.2 CO the active site is a (enzyme-Cys)2(CN)Ni(micro-enzyme-Cys)2Fe(CN)3(CO) centre 655890 1.12.1.2 Co2+ NAD+ reduction with H2 is completely dependent on the presence of divalent metal ions Ni2+, Co2+, Mg2+ or Mn2+ or of high salt concentrations between 500-1500 mM 439702 1.12.1.2 cyanide enzyme contains four cyanides in its active site, one of which is responsible for the insensitivity towards oxygen 656298 1.12.1.2 Fe Ni-Fe enzyme. Analysis of the Ni-Fe cofactor revealed a nonstandard structure, (CN)(O)3NiII(mu-CysS)2FeII(CN)3(CO) 674165 1.12.1.2 Fe Ni-Fe hydrogenase. Monitoring of the structure and oxidation state of its metal centers during H2 turnover 672067 1.12.1.2 Fe the (CO)3Fe(II) site is octahedral. An octahedral iron and a distorted square pyramidal nickel are linked by three bridging ligands 706499 1.12.1.2 Fe2+ - 689959 1.12.1.2 Fe2+ contains iron in the catalytic core 687407 1.12.1.2 Fe2+ enzyme contains a [Ni-Fe] cluster 656298 1.12.1.2 Fe2+ the active site is a (enzyme-Cys)2(CN)Ni(micro-enzyme-Cys)2Fe(CN)3(CO) centre 654562, 655890, 656298 1.12.1.2 Iron 11.5 iron atoms per enzyme molecule, enzyme contains 2 [4Fe-4S] and 2 [2Fe-2S] clusters 439709 1.12.1.2 Iron 13.6 iron atoms per enzyme molecule 439703 1.12.1.2 Iron enzyme contains multiple iron-sulfur clusters, [4Fe-4S] or [2Fe-2S] 656734 1.12.1.2 Iron Fe2+ stabilizes 439693 1.12.1.2 Iron no increase of activity by addition of Co2+, Mn2+, Ni2+ or Fe2+ 439699 1.12.1.2 Iron non-heme iron protein 439699, 439703, 439706 1.12.1.2 Iron the active site iron atom has a standard ligation, i.e., one CO and two cyanide ligands 724910 1.12.1.2 Iron the diaphorase contains 3 [2Fe-2S] cluster, the hydrogenase subunit HoxY contains one [2Fe-2S] cluster coordinated by 9 Cys residues 654782 1.12.1.2 Iron the enzyme contains at least one [4Fe4S]+ and at least one [2Fe2S]+ cluster 704606 1.12.1.2 Iron [NiFe] hydrogenases carry a metal centre composed of Fe and Ni atoms at the active site 684181 1.12.1.2 Iron [NiFe]-hydrogenase, the ratio of iron to nickel is 13 gatom Fe/1 gatom Ni. The absorption spectrum is typical of iron-sulfur proteins having [4Fe-4S] clusters 744926 1.12.1.2 K+ activates 439701 1.12.1.2 Mg2+ bound to the hydrogenase subunits 654782 1.12.1.2 Mg2+ NAD+ reduction with H2 is completely dependent on the presence of divalent metal ions Ni2+, Co2+, Mg2+ or Mn2+ or of high salt concentrations between 500-1500 mM 439702 1.12.1.2 Mg2+ NAD-reduction: no linear kinetics in absence of metals, 0.5 mM Ni2+ and 5 mM Mg2+ required 439701 1.12.1.2 Mg2+ stabilizes 439693 1.12.1.2 Mn2+ NAD+ reduction with H2 is completely dependent on the presence of divalent metal ions Ni2+, Co2+, Mg2+ or Mn2+, or of high salt concentrations of 500-1500 mM 439702 1.12.1.2 Mn2+ stabilizes 439693 1.12.1.2 additional information metalloenzyme 654388, 654821 1.12.1.2 additional information no increase of activity by addition of Co2+, Mn2+, Ni2+ or Fe2+ 439699 1.12.1.2 additional information stimulation of activity by salt is greater the less chaotrophic the anion 439702 1.12.1.2 Ni Ni-Fe enzyme. Analysis of the Ni-Fe cofactor revealed a nonstandard structure, (CN)(O)3NiII(mu-CysS)2FeII(CN)3(CO). The unusual ligation of the Ni by only two thiols plus further (C,O) ligands seems to be a prerequisite of the exceptionally rapid activation of the SH by NADH, involving the loss of an oxygen ligand from the Ni. Evidence for the binding of hydrogen to the open coordination site at Ni has been obtained. The hydrogen cleavage reaction seems not to involve a Ni-C state (Ni(III)-H-). The CN ligand at the Ni may be involved in establishing both rapid activation and oxygen-insensitive catalytic behavior in the SH. Possibly, one important function of the CN is stabilization of the Ni(II) oxidation state throughout the catalytic cycle of hydrogen cleavage 674165 1.12.1.2 Ni Ni-Fe hydrogenase. Monitoring of the structure and oxidation state of its metal centers during H2 turnover 672067 1.12.1.2 Ni2+ - 689959 1.12.1.2 Ni2+ 2 nickel atoms per enzyme molecule 439707 1.12.1.2 Ni2+ 3.8 nickel atoms per enzyme molecule 439703 1.12.1.2 Ni2+ below 0.06 mol Ni2+ per mol of enzyme 656734 1.12.1.2 Ni2+ contains nickel in the catalytic core 687407 1.12.1.2 Ni2+ enzyme contains a [Ni-Fe] cluster 654782, 656298 1.12.1.2 Ni2+ highest specific activity with NiCl2, optimal concentration: 1 mM 439702 1.12.1.2 Ni2+ NAD+ reduction with H2 is completely dependent on the presence of divalent metal ions Ni2+, Co2+, Mg2+ or Mn2+ or of high salt concentrations between 500-1500 mM 439702 1.12.1.2 Ni2+ NAD-reduction: no linear kinetics in absence of metals, 0.5 mM Ni2+ and 5 mM Mg2+ required 439701 1.12.1.2 Ni2+ nickel is essential for the catalytic activity of the enzyme 439706, 439707 1.12.1.2 Ni2+ nickel protein 439703 1.12.1.2 Ni2+ presence of a Ni(CN)Fe(CN)3(CO) active site is suggested 439712 1.12.1.2 Ni2+ take-up/release of substrates may occur at the Ni site. Flexible coordination structures at Ni may be responsible for the interconversion between H2 and (2H+) as the unique function of the [NiFe] hydrogenase. The coordination mode of the Ni(II) center can vary from square planar, to distorted square pyramidal, and to octahedral geometries, dependent on the nature of the ligands. An octahedral iron and a distorted square pyramidal nickel are linked by three bridging ligands 706499 1.12.1.2 Ni2+ the active site is a (enzyme-Cys)2(CN)Ni(micro-enzyme-Cys)2Fe(CN)3(CO) centre 655890 1.12.1.2 Ni2+ the active site is a (enzyme-Cys)2(CN)Ni(micro-enzyme-Cys)2Fe(CN)3(CO) centre, H2 activation solely takes place on Ni2+ 654562, 656298 1.12.1.2 Nickel [NiFe] hydrogenases carry a metal centre composed of Fe and Ni atoms at the active site 684181 1.12.1.2 Nickel [NiFe]-hydrogenase, the ratio of iron to nickel is 13 gatom Fe/1 gatom Ni 744926