 for enzyme-substrate reaction was further discussed and analyzed by a series of follow-up studies.A detailed comparison between the simplified Alberty-Hammes-Eigen's model (a) and the Chou's model (b) in calculating the diffusion-controlled reaction rate of enzyme with its substrate, or the upper limit of enzyme-substrate reaction, was elaborated in the paper.Kinetically perfect enzymes have a specificity constant, "k"cat/"K"m, on the order of 108 to 109 M−1 s−1.