Essential Loop Dynamics Modulates Catalytic Activity in alpha-Chymotrypsin

摘要

Conformational dynamics of macromolecules including enzymes are essential for their function. The present work reports on the role of essential dynamics in alpha-chymotrypsin (CHT) which correlates with its catalytic activity. Detailed optical spectroscopy and classical molecular dynamics (MD) simulations were used to study thermal stability, catalytic activity and dynamical flexibility of the enzyme. The study of the enzyme kinetics reveals optimum catalytic efficiency at 308 K. Polarization gated fluorescence anisotropy with 8-anilino-1-napthelene sulfonate (ANS) have revealed increasing flexibility of the enzyme with an increase in temperature. Examination of the structure of CHT reveal the presence of five loop regions (LRs) around the catalytic S1 pocket. MD simulations have indicated that flexibility increases concurrently with temperature which decreases beyond an optimum temperature. Principal component analysis (PCA) of the eigenvectors manifests essential dynamics and gatekeeping role of the five LRs surrounding the catalytic pocket which controls the enzyme activity.