Cyanide inhibition of the catalase system

Abstract

The concentration of cyanide, I 50, required to bind or inhibit 50% of bacterial catalase heme groups has been determined in the presence and absence of hydrogen peroxide. The difference in values of I 50 obtained by kinetic and spectroscopic studies is approximately 40% and agrees with that predicted from the analytical solution for the kinetics of inhibition by cyanide. At 13.6 ° the dissociation constant is 4.78 ± 1.20 × 10 −6 M from inhibition data and 4.60 × 10 −6 M ± 1.36 × 10 −6 M from spectrophotometric data. The heat of the reaction between cyanide and catalase is approximately 19,600 cal./mole.