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Title: Cyanide inactivation of hydrogenase from Azotobacter vinelandii

The effects of cyanide on membrane-associated and purified hydrogenase from Azotobacter vinelandii were characterized. Inactivation of hydrogenase by cyanide was dependent on the activity (oxidation) state of the enzyme. Active (reduced) hydrogenase showed no inactivation when treated with cyanide over several hours. Treatment of reversibly inactive (oxidized) states of both membrane-associated and purified hydrogenase, however, resulted in a time-dependent, irreversible loss of hydrogenase activity. The rate of cyanide inactivation was dependent on the cyanide concentration and was an apparent first-order process for purified enzyme (bimolecular rate constant, 23.1 M{sup {minus}1} min{sup {minus}1} for CN{sup {minus}}). The rate of inactivation decreased with decreasing pH. ({sup 14}C)cyanide remained associated with cyanide-inactivated hydrogenase after gel filtration chromatography, with a stoichiometry of 1.7 mol of cyanide bound per mol of inactive enzyme. The presence of saturating concentrations of CO had no effect on the rate or extent of cyanide inactivation of hydrogenases. The results indicate that cyanide can cause a time-dependent, irreversible inactivation of hydrogenase in the oxidized, activatable state but has no effect when hydrogenase is in the reduced, active state.
Authors:
;  [1]
  1. (Univ. of California, Riverside (USA))
Publication Date:
OSTI Identifier:
6936059
DOE Contract Number:
FG03-84ER13257
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Bacteriology; (USA); Journal Volume: 171:6
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; 59 BASIC BIOLOGICAL SCIENCES; AZOTOBACTER; SENSITIVITY; CYANIDES; TOXICITY; HYDROGENASES; INACTIVATION; CARBON 14 COMPOUNDS; ENZYME ACTIVITY; TRACER TECHNIQUES; BACTERIA; ENZYMES; ISOTOPE APPLICATIONS; LABELLED COMPOUNDS; MICROORGANISMS; OXIDOREDUCTASES 560300* -- Chemicals Metabolism & Toxicology; 550201 -- Biochemistry-- Tracer Techniques