Thermochemistry of the N-acetylphenylalanine methylester hydrolysis reaction catalyzed by α-chymotrypsin

Abstract

The enthalpy of the reaction ▪ is found to be Δ H 1 = −4.81 ± 0.10 kJ mol −1 (0.05 M phosphate buffer, pH 7.0, 298.15 K). Using values of the enthalpies of ionization of the buffer solution (Δ H i buffer = −3.98 ± 0.20 kJ mol −1) and N-acetylphenylalanine (Δ H i acphen = −2.46 ± 0.09 kJ mol −1), found experimentally, the enthalpy of the following hydrolysis reaction has been calculated ▪ Δ H 2 = Δ H 1 − Δ H i buff − Δ H i acphen = +1.63 ± 0.25 kJ mol −1, as applied to the reaction of undissociated compounds in aqueous solution. The enthalpy of reaction (2) is compared to the enthalpies of other hydrolysis reactions in compounds with ester bonds.