Different primary specificity of porcine pancreatic beta-kallikrein-B and bovine beta-trypsin. A comparative steady-state and pre-steady-state study.

The values of pre-steady-state and steady-state parameters for the beta-trypsin catalyzed hydrolysis of Z-Arg-ONp and Z-Lys-ONp are superimposable between pH 2.4 and 8. At variance, the kinetic parameters for the beta-kallikrein-B catalyzed hydrolysis of Z-Arg-ONp are more favourable than those observed for Z-Lys-ONp and depend on different pKa values. The different primary specificity and the catalytic behaviour of beta-trypsin and beta-kallikrein-B reflect structural differences at their S1 subsite, especially at level of the 226 residue as well as the 217-220 segment.