A study of heat of formation of acetyl-alpha-chymotrypsin intermediate by stopped flow calorimetry.
The catalytic hydrolysis of p-nitrophenyl acetate by alpha-chymotrypsin was studied by stopped-flow calorimetry and spectrophotometry at pH 8.0 and 25 degrees C. The initial burst and subsequent 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 in equilibrium ES leads to acetyl-E + P1 (p-nitrophenol) leads to E + P1 + acetic acid, the enthalpy change of formation of the acetyl enzyme from ES complex was estimated to be -29 kJ . mol-1.
D002151:Calorimetry / Q000379:methods; D002918:Chymotrypsin / Q000378:metabolism*; D009596:Nitrophenols / Q000378:metabolism*; D013053:Spectrophotometry; D013816:Thermodynamics
D009596:Nitrophenols; D002918:Chymotrypsin