抄録
N-Acetyl-β-D-glucosaminidase [EC 3.2.1.30] of Asp. oryzae hydrolyzed N-acetylchitopentaitol from nonreducing end. The study of enzymatic hydrolysis rates of N-acetylchito-oligosaccharides and reduced N-acetyl-chito-oligosaccharides showed that the active site of the enzyme consisted of two subsites.
Values of free energy of binding to the enzyme of phenyl N-acetyl-β-D-glucosaminide and its deoxy analogues were calculated from the Michaelis constants. The contribution to the binding of each hydroxyl group, defined as partial binding free energy, was estimated from the difference of the binding energies between phenyl N-acetyl-β-D-glucosaminide and its deoxy analogues. Contribution to the binding of acetamido and phenoxy group was obtained from the inhibitor constants of phenyl β-D-glucoside and 2-acetamido-2-deoxy-1, 5-anhydroglucitol (1-deoxy-N-acetylglucosamine), respectively. These results suggested an existence of four hydrogen bonds between phenyl N-acetyl-β-D-glucosaminide and the enzyme, two of them being at acetamido of C2 another two at hydroxyl of C3 and C4. The sum of the partial binding free energies was nearly equal to the unitary binding free energy of phenyl N-acetyl-β-D-glucosaminide.
