Subsite Structure of Rhizopus niveus Glucoamylase,Estimated with the Binding Parameters for Maltooligosaccharides

Based on K_d and K_i for maltosaccarides G_n (n = 1 ± 7) and on a specified mode of their binding, the intrinsic affinities A₁, A₂, –, A_i at subsites i (i = 1 ± 5), were tried to estimate for glucoamylase from Rhizopus niveus. Previously, we have evaluated the apparent values A_i using K_m and k₀ on the enzyme-catalyzed hydrolysis for G_n, where A₁ is nearly 0 kcal/mol. Thus A₁, which was found here 3.3 kcal/mol, may be cancelled out with the heat, which is consumed for the hydrolytic cleavage of a substrate glucosyl bond.