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Free keywords:
Hydrogenase; Iron-guanylylpyridinol cofactor; Methanogenic archaea; Inhibitor; Infrared spectra
Abstract:
[Fe]-Hydrogenase catalyzes the reversible activation of H(2). CO and CN(-) inhibit this enzyme with low affinity (K(i)≅0.1 mM) by binding to the iron site of the bound iron-guanyrylpyridinol cofactor. We report here that isocyanides, which are formally isoelectronic with CO and CN(-), strongly inhibit [Fe]-hydrogenase (K(i) as low as 1 nM). The [NiFe]- and [FeFe]-hydrogenases tested were not inhibited by isocyanides. UV-Vis and infrared spectra revealed that the isocyanides bind to the iron center of [Fe]-hydrogenase. The inhibition kinetics are in agreement with the proposed catalytic mechanism, including the open/closed conformational change of the enzyme.
