[Active sites of enzymes: stereochemistry and dynamics]

The concept of an enzyme active site as of an integrated network system, which is substantiated by multipoint contacts between constituents, is presented. The conformational and electronic state of an enzyme active site supposed to be determined by hydrogen bonds network, which connects different subsites and components of the active site. The substrate specificity of an enzyme is achieved by means of hydrogen bonds formation between the protein and nonreacting fragment of the substrate molecule. As a consequence, reacting fragment of a substrate and those of an enzyme are locked in the configuration close to that of the transition state for the reaction. Stereochemical and dynamical aspects of ribonucleases specificity are considered in the framework of the concept. A molecular mechanism for the enzyme-substrate recognition is suggested.