A kinetic study on the diffusion-coupled reaction of a basic horseradish peroxidase adsorbed on the...

The rate of reactions of a basic horseradish peroxidase adsorbed on the carboxymethylcellulose membrane was measured spectrophotometrically by monitoring the state of the enzyme. For the reactions with hydrogen peroxide and cyanide dissolved in media the diffusion process was rate limiting both in the static and flowing media, and kinetic features of the enzyme were masked. The rate of CO recombination of the ferrous enzyme was measured by flash photolysis in the static media containing varying amounts of CO. Apparently, the initial rate of CO recombination was no more affected by the diffusion factor, and the second order rate constant could be measured for the reaction of the enzyme adsorbed on the membrane. The value was about 70% of that obtained from the enzyme in solution and exhibited the same pH dependence as did the value for the enzyme in solution. The difference of the reaction pattern between the enzymes on the membrane and in solution became distinct when flash photolysis was applied to the reaction system without free CO in the medium. The kinetic data were analyzed by computer simulation.