Kinetic studies of pepsin active site model compound and porcine pepsin

The kinetic parameters for the hydrolysis of the heptapeptide Pro-Thr-Glu-P he-(4-NO2)Phe-Arg-Leu by the pepsin model compound tetrabutylammonium monos alt of m-aminobenzoic acid diamide of fumaric acid (TBA m-FUM) and porcine pepsin were determined using a spectrophotometric technique. According to t he DeltaS(not equal) values obtained, in the transition state the inner mot ion in the TEA m-FUM-heptapeptide complex is more restricted than that in t he pepsin-heptapeptide complex. The modal compound TEA m-FUM can cause a cl eavage of the Phe(4-NO2)Phe bond in the substrate molecules following a mec hanism similar as that suggested for pepsin, but its catalytic activity is much lower. Copyright (C) 2001 John Wiley & Sons, Ltd.