sentences:  Through the kinetic isotope effect much insight can be gained as to what the transition state looks like of an enzyme-catalyzed reaction and guide the development of transition state analogs.Computational approaches have been regarded as a useful tool to elucidate the mechanism of action of enzymes.Molecular mechanics itself can not predict the electron transfer which is the fundamental of organic reaction but the molecular dynamics simulation provide sufficient information considering the flexibility of protein during catalytic reaction.