[Active center of glycoamylase from Aspergillus awamori]

The maltooligosaccharides--triose, tetrose, pentose and hexose have been obtained by fractionation of partially hydrolyzed cyclohexamylose. The values of free energies for the binding of the first six sites of glucose residue binding in the enzyme active center were calculated according to the Hiromi model and were found to be equal to -0.6, -4.5, -1.68, -0.66, -0.25 and +-0.06 kcal/mole, respectively. The Hiromi model was extrapolated to p-nitrophenyl-alpha-D-glucoside, p-nitrophenyl-alpha-D-maltoside and methyl-alpha-D-glucoside. The energies for nitrophenol binding for the second, third and fourth centers and of the methyl group binding for the second and third centers were determined. The value of universal catalytic constant kcat is equal to 47.9 s-1 at 37 degrees.