Quantum-Chemical Study of Catalytic Mechanism of Serine Proteases (III) / 昆明医科大学学报

ABSTRACT

In this paper, the model system of proton transfer with the water molecule as an intermediate acceptor of Ser-195 was suggested and analysed by the CNDO/2 method. The acylation activation barrier of this system was shown to restrict the stage of synchronous transfer of the Ser-195 alcoholic proton and the water molecule proton hydrogen bound to His-57 N~(?_2)-atom to the water molecule oxygen atom and the N~(?_2)-atom, respectively. The substrate protonation in the case of the model system with the water molecule as the in ermediate acceptor was demonstrated to begin before the completion of the tetrahedral inermediate substance, only the protonated form of the tetrahedal intermediate being shown. A lypothesis of considering the role of this water molecule as a nuclephilic reagent in the leacylation stage is presented.