Galactosylation Thermodynamics of E. Coli Beta-Galactosidase by Onpg and Pnpg

Michaelis-Menten analysis of the hydrolyses of ONPG and PNPG by E. coli beta-galactosidase were performed from 5.5 to 45 degree C. Analysis of the T-dependence of KM and kcat reveals the thermodynamics for formation of the E / S complex and attainment of the galactosylation transition state, respectively. While the binding and transition state free energies are similar for each substrate, the enthalpic and entropic contributions are found to differ substantially.