Open AccessThe Reaction of the Iron‐Sulfur Protein Hydrogenase with Carbon Monoxide
Author(s) -
Thauer Rudolf K.,
Käfer Barbara,
Jungermann Kurt,
Zähringer Marianne
Publication year - 1974
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1974.tb03358.x
Subject(s) - carbon monoxide , hydrogenase , chemistry , cyanide , inorganic chemistry , reaction rate constant , dissociation (chemistry) , sulfur , steady state (chemistry) , carbon monoxide dehydrogenase , kinetics , hydrogen , catalysis , organic chemistry , physics , quantum mechanics
The iron‐sulfur protein hydroenase from Clostridium pasteurianum was shown to be specifically inhibited by carbon monoxide. Cyanide (10 mM), azide (10 mM), and fluoride (10 mM) were without effect. The inhibition of hydrogenase by carbon monoxide was studied under pre‐steady‐state and under steady‐state conditions. The data obtained from both studies indicate a 1:1 stoichiometry of the reversible reaction between an independent active site of hydrogenase and carbon monoxide. The second‐order rate constant of the formation ( k +1 ) and the first‐order rate constant of the dissociation ( k −1 ) of the hydrogenase · carbon‐monoxide complex at pH values between 6.5 and 8.5 and at 25°C were found to be 5.7 s −1 mM −1 and 0.013 s −1 , respectively. The equilibrium constant K was calculated from pre‐steady‐state data to be 440 mM −1 and from steady‐state data to be 420 mM −1. The carbon monoxide inhibition of hydrogenase could be reversed bylight. The light sensitivity indicates that in the active site iron is being attacked by carbon monoxide.