[Kinetics of peroxidase recombination with carbon dioxide in the +20 to -70 degree C temperature interval]

Using flash photolysis, horseradish peroxidase rebinding of carbon monoxide has been observed in the temperature range between 20 and -70 degrees C. A lag-period of about 50 ms immediately after photodissociation takes place. This lag-period is assumed to be due to the formation of the intermediate protein form with the low reactivity. Following rebinding is bimolecular process with the rate constant 4 x 10(3) M-1 S-1 usually observed for the peroxidase reaction with carbon monoxide. For some peroxidase molecules (about 10 per cent) rebinding of carbon monoxide is CO-concentration independent monomolecular process, which implies, apparently, ligands in these molecules do not leave the protein after photodissociation.