Characterization of a control switch in chymotrypsin

Area of Science:

• Biochemistry
• Enzyme kinetics
• Protein conformational changes

Background:

• Chymotrypsin is a key digestive enzyme.
• Understanding its conformational changes is crucial for enzyme function.
• Substrate specificity plays a role in enzyme regulation.

Purpose of the Study:

• To determine kinetic and thermodynamic parameters of chymotrypsin's conformational change.
• To elucidate the mechanism of conformational regulation.
• To identify key residues involved in catalytic site activation.

Main Methods:

• Chemical relaxation method used to study binding kinetics.
• Analysis of concentration-dependent relaxation times and amplitudes.
• Investigation of pH and temperature dependencies.

Main Results:

• Individual step rate constants, enthalpies, and entropies were evaluated.
• Ionizing groups involved in regulating conformational steps identified.
• A detailed mechanism for conformational change function proposed.

Conclusions:

• ASp-194 acts as a switch, modulating catalytic activity.
• This switch mechanism involves movement between His-57 and Ile-16.
• The enzyme's catalytic site is sensitive to pH and temperature.