Binding of the bovine basic pancreatic trypsin inhibitor (Kunitz) to human urinary kallikrein and to porcine pancreatic beta-kallikreins A and B.

Centro di Biologia Molecolare del C.N.R. e Istituto di Chimica Facoltà di Medicina e Chirurgia Università di Roma “La Sapienza” Piazzale Aldo Moro 2, 00185 Roma, Italy
Journal of Molecular Biology (Impact Factor: 3.91). 08/1984; 176(3):425-30. DOI: 10.1016/0022-2836(84)90498-4
Source: PubMed

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.

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