[Analysis of kinetic isotope effects in H2O-D2O mixtures in enzymatic catalysis: detection of conformation-dynamic processes]

An analysis was carried out of Gross-Butler type equations describing relationship between deuterium isotope effect in reactions with proton transfer and deuterium concentration in the medium. It has been shown that with all possible coefficient values of isotopic fractionation of enzyme functional group protons the shape of indicated relationships qualitatively differs from the experimentally observed one for myosin hydrolysis of ATP. This discrepancy as well as uniform nonlinear change of myosin denaturation temperature and of kinetic isotope effect in myosin hydrolysis of ATP on deuterium fraction in solution give evidence of D2O effect as a solvent and point to an essential role of conformational - dynamic processes in the course of enzymic catalysis with myosin.