A high-molecular mass derivative of trypsin-kallikrein inhibitor for potential medical use. II. Study of inhibitory activity.

Three derivatives of poly[alpha-N beta-(2-hydroxyethyl)-DL-asparagine, beta-N alpha-(2-hydroxyethyl)-DL-asparagine] were used as soluble carrier polymers for binding the trypsin-kallikrein inhibitor (TKI). In addition to the parent polymer an anionic derivative with 19.2 mol of carboxyl groups/100 mol of residues and a hydrophobized derivative with 18.0 mol of butyl groups/100 mol of residues were also used. All carriers contained 6.6 mol of 2-(4-aminobenzamido)ethyl residues/100 mol which were used for the binding after diazotation. All derivatives retained a high inhibitory activity toward trypsin and chymotrypsin whereas the effect on kallikrein was substantially reduced. The kinetic constants were estimated under the simplifying assumption, that classical kinetic equations for the enzyme-inhibitor interaction may be applied. The equilibrium dissociation constants (5 X 10(-9) mol/l) and association rate constants (1 X 10(5) l X mol-1 X s-1) with respect to trypsin are unaffected by the two chemical modifications of the carrier. The increase in the equilibrium dissociation constant (compared to native TKI) is probably a result of the decreasing strength of the enzyme-inhibitor complex rather than a manifestation of reduced rate of diffusion of the enzyme to the active center of the polymer-bound inhibitor.