[Soluble high molecular weight derivatives of pancreatic inhibitors. Kinetic-thermodynamic studies of inhibitors linked to differently charged matrices]

Abstract

The effects of electrostatic charge of the matrix on the pH-dependence of interactions of commercial trypsin with preparations of pancreatic inhibitor modified by soluble polysaccharide coupling were studied. It was shown that the rate constants of trypsin association with native and modified pancreatic inhibitor preparations as well as the rate constants of dissociation of their complexes and, consequently, the inhibition constants are identical. The invariability of the rate constants for the association reaction after the increase in the molecular weight of pancreatic inhibitor may be probably accounted for by the fact that the limiting step of a stable trypsin-inhibitor complex formation is not controlled by diffusion. Thermal denaturation of pancreatic inhibitor preparations modified by binding to polysaccharides (pH 4.7--8.0, 97 degrees C) suggests an essential role of the negative charge of matrix in stabilization of the protein inhibitor globule.