title: The role of binding subsite A in reactions catalyzed by hen egg-white lysozyme.
abstract: The role of binding subsite A, located at the terminal of the six binding subsites of hen egg-white lysozyme, in substrate binding and catalytic reactions was investigated by kinetic studies using a chemical modification method. Computer simulation showed that, although subsite A participates in the binding of the substrate, a decrease in the affinity of subsite A to the sugar residue does not cause a lowering of the rate of substrate consumption but changes the mode of the reaction by changing the distribution of the products formed. The binding free energies of subsites for Asp-101-modified lysozymes were estimated by data-fitting from the experimental time-courses. The contribution of Asp-101 in hen egg-white lysozyme to the substrate binding at subsite A was estimated to correspond to a binding free energy of about -3 kJ/mol, 30% of the total binding free energy of subsite A. Modification of Asp-101 affected not only the binding free energy of subsite A but also that of subsite C.
mesh_terms: D000818:Animals; D001665:Binding Sites; D003201:Computers; D004529:Egg White; D007700:Kinetics; D009113:Muramidase; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D009113:Muramidase