title: Unusual reaction of [NiFe]-hydrogenases with cyanide.
abstract: Cyanide reacts rapidly with [NiFe]-hydrogenases (hydrogenase-1 and hydrogenase-2 from Escherichia coli) under mild oxidizing conditions, inhibiting the electrocatalytic oxidation of hydrogen as recorded by protein film electrochemistry. Electrochemical, EPR, and FTIR measurements show that the final enzyme product, formed within a second (even under 100% H2), is the resting state known as Ni-B, which contains a hydroxido-bridged species, Ni(III)-μ(OH)-Fe(II), at the active site. "Cyanide inhibition" is easily reversed because it is simply the reductive activation of Ni-B. This paper brings back into focus an observation originally made in the 1940s that cyanide inhibits microbial H2 oxidation and addresses the interesting mechanism by which cyanide promotes the formation of Ni-B. As a much stronger nucleophile than hydroxide, cyanide binds more rapidly and promotes oxidation of Ni(II) to Ni(III); however, it is quickly replaced by hydroxide which is a far superior bridging ligand.
authors.affiliation: Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford , South Parks Road, Oxford OX1 3QR, United Kingdom.
authors.forename: Suzannah V
authors.initials: SV
authors.lastname: Hexter
authors.forename: Min-Wen
authors.initials: MW
authors.lastname: Chung
authors.forename: Kylie A
authors.initials: KA
authors.lastname: Vincent
authors.forename: Fraser A
authors.initials: FA
authors.lastname: Armstrong
mesh_terms: D000693:Anaerobiosis; D003486:Cyanides / Q000737:chemistry*; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry*
chemical_list: D003486:Cyanides; D029968:Escherichia coli Proteins; C043296:nickel-iron hydrogenase; D006864:Hydrogenase; C000602631:hydrogenase 1, E coli; C481721:hydrogenase 2, E coli