A Study of Heat of Formation of Acetyl-α-Chymotrypsin Intermediate by Stopped Flow Calorimetry

Abstract

The catalytic hydrolysis of p-nitrophenyl acetate by α-chymotrypsin was studied by stoppedflow calorimetry and spectrophotometry at pH 8.0 and 25°C. The initial burst and sub-
sequent steady state of the reaction were observed by rapid calorimetry and spectrophotometry. Based on the three-step mechanism established for the enzymatic reaction,
E +S_??_ES→acetyl-E+P₁ (p-nitrophenol)→E+P₁+acetic acid,
the enthalpy change of formation of the acetyl enzyme from ES complex was estimated to be -29 kJ•mol^-1.