title: Binding of the trypsin inhibitor from white mustard (Sinapis alba L.) seeds to bovine beta-trypsin: thermodynamic study.
abstract: The effect of pH and temperature on the association equilibrium constant (Ka) for the binding of the trypsin inhibitor from white mustard (Sinapis alba L.) seeds (MTI) to bovine beta-trypsin (EC 3.4.21.4) has been investigated. On lowering the pH from 9 to 3, values of Ka for MTI binding to bovine beta-trypsin decrease thus reflecting the acid-pK and -midpoint shifts, upon inhibitor association, of two independent ionizable groups, and of a three-proton transition, respectively. At pH 8.0, values of thermodynamic parameters for MTI binding to bovine beta-trypsin are: Ka = 4.5 X 10(8)M-1, delta G0 = -11.6 kcal/mol, and delta S0 = +53 entropy units (all at 21 degrees C); and delta H0 = +4.1 kcal/mol (temperature independent between 5 degrees C and 45 degrees C). Binding properties of MTI to bovine beta-trypsin have been analyzed in parallel with those concerning macromolecular inhibitor association to serine (pro)enzymes.
mesh_terms: D000818:Animals; D002417:Cattle; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009149:Mustard Plant; D010946:Plants, Medicinal; D011485:Protein Binding; D012639:Seeds; D013816:Thermodynamics; D014357:Trypsin / Q000378:metabolism*; D014361:Trypsin Inhibitors / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D014361:Trypsin Inhibitors; D014357:Trypsin