Characterization for the Active Site of β-Glucosidase fromAspergillus niger: Studied by the Inhibition Kinetics and the Fluorescence Spectrophotometric Titration with Glyco-Ligands

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β-Glucosidase (EC 3 .2.2.21, βGA) from Aspergillus niger was confirmed to be a monomer of Mw 137, 000. A glyco-ligand glucono-1: 5-lactone (GLN) inhibits the RGA-catalyzed reaction competitively with cellobiose. Formation of the GLN-βGA complex was confirmed by the fluorescence-spectro photometric titration (K<SUB>d</SUB>, 10 μM) based on Trp residue. Galactose also competitively inhibits the β GA-catalyzed reaction, but a change in the fluorescence was not produced by its binding. It may be concluded that GLN, a transition-state analogue, is bound at subsite 1, where a Trp residue is located that is concerned with the βGA reaction. Galactose is bound probably at the subsite, different from subsite 1. These findings may be intimately related to the substrate specificity of β-glucosidase.
日本応用糖質科学会の論文