KINETICS OF THE INHIBITION OF HUMAN-LEUKOCYTE ELASTASE BY EGLIN FROM THE LEECH HIRUDO-MEDICINALIS

The rate constants for the inhibition of human leukocyte elastase by eglin from the leech Hirudo medicinalis were determined by using a pre-steady-state kinetic approach. The kon and koff for complex-formation and dissociation were 1 .times. 106 per M per s and 8 .times. 10-4 per s, respectively. Ki was calulated as the ratio koff/kon = 8 .times. 10-10 M; the binding of eglin to elastase was reversible and the inhibition mechanism was of the fully competitive type. The mechanistic properties of the system and the biological significance of the rate constants are discussed.