Evaluation of inhibitor constants and alkylation rates for a series of thrombin affinity labels.

The kinetics for the inactivation of thrombin (EC 3.4.21.5) by a series of peptides containing C-terminal arginyl chloromethane in the presence of substrate were determined. The inhibitor effectiveness was analysed so as to allow for both the evaluation of the affinity with which the enzyme binds the inhibitor before irreversible modification and also the rate of covalent-bond formation between enzyme and inhibitor. The results obtained show that the observed large range in inhibitor effectiveness can be accounted for almost entirely by marked differences in affinity, with only small variations in rates of formation of covalent complex.