QCMEE study of the reductive half-reaction of glucose oxidase

A quantum-chemical model for electrostatic effects (QCMEE) in biomolecules is applied to the reductive half-reaction of glucose oxidase. The electrost atic influence of the enzyme on its active center is estimated. Six differe nt states of protonation of the active center are compared by a hybrid meth od where the relative energies of the active center states are calculated a b initio and the relative energies of the electrostatic interaction between the active center and the rest enzyme are calculated by the quantum-chemic al model. These model calculations comprise the total enzyme consisting of 8784 atoms. It is found that the double protonation of the histidine group His516 is greatly stabilized by the electrostatic interaction with the rest enzyme. This explains the experimental findings that His516 is essential f or the function of the enzyme. (C) 2000 John Wiley & Sons, Inc.