title: Binding of the bovine basic pancreatic trypsin inhibitor (Kunitz) to human urinary kallikrein and to porcine pancreatic beta-kallikreins A and B.
abstract: The effect of pH and temperature on the association equilibrium constant (Ka) for bovine basic pancreatic trypsin inhibitor (BPTI, Kunitz inhibitor) binding to human urinary kallikrein and porcine pancreatic beta-kallikreins A and B has been investigated. Ka values decrease with decreasing pH, reflecting the acid-midpoint and pK shifts, upon BPTI binding, of a three-proton co-operative transition, between pH 3 and 5, and of a single ionizable group, between pH 5 and 9. At pH 8, the values of delta H degree (between 7 degrees C and 42 degrees C) and delta S degree (at 21 degrees C) for BPTI binding to the glandular kallikreins considered were determined. In particular, the delta H degree values have been found to be independent of temperature and the following values have been obtained by van't Hoff plots: +1.8 kcal/mol, +2.3 kcal/mol and +2.4 kcal/mol (1 kcal = 4184 J) for the inhibitor binding to human urinary kallikrein and porcine pancreatic beta-kallikreins A and B, respectively. Considering the known molecular structures of free porcine pancreatic beta-kallikrein A and BPTI, and of their complex, the stereochemistry of the enzyme : inhibitor contact regions was analysed for the three serine proteinases, in relation to their respective types of behaviour.
mesh_terms: D000818:Animals; D007611:Aprotinin / Q000378:metabolism*; D001665:Binding Sites; D002417:Cattle; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007610:Kallikreins / Q000378:metabolism* / Q000652:urine; D007700:Kinetics; D013552:Swine; D013696:Temperature; D013816:Thermodynamics
chemical_list: D007611:Aprotinin; D007610:Kallikreins