IRREVERSIBLE INACTIVATION OF CALDARIOMYCES-FUMAGO CHLOROPEROXIDASE BYHYDROGEN-PEROXIDE - A KINETIC-STUDY IN CHLORIDE AND BROMIDE SYSTEMS

The rate constants for the H2O2-induced irreversible inactivation (k(i nact)) of chloroperoxidase from Caldariomyces fumago evaluated from th e analysis of complete kinetic curves of chlorination or bromination o f monochlorodimedon were found to follow the rate law k(inact)=k[H2O2] /(K+[H2O2]) with k=0.009+/-0.002 and 0.0095+/-0.0010 s(-1) and K=(13+/ -4)x10(-3) and (9+/-2)x10(-3) M in the presence of 0.01 M chloride and bromide, respectively, at pH 2.75 and 25 degrees C. The data show tha t chloroperoxidase investigated is more than by a factor of 10 less re sistant toward hydrogen peroxide compared to horseradish peroxidase. T he possible reason for it and the biotechological implications are bri efly discussed.