Title:A Single Amino Acid Residue Determines the Ratio of Hydrolysis to Transglycosylation Catalyzed by β-Glucosidases
Volume: 20
Issue: 1
Author(s): M.A. Frutuoso and S.R. Marana
Affiliation:
Keywords:
β-glucosidases, glycoside hydrolases, oligosaccharides synthesis, Spodoptera frugiperda, Tenebrio molitor, transglycosylation, substrate
Abstract: The propensity to catalysis of transglycosylation of the β-glucosidase Tmβgly is higher than for Sfβgly.
Moreover the propensity to catalysis of transglycosylation is directly proportional to the substrate concentration for
Tmβgly, whereas for Sfβgly it is constant. For instance, 60% of a Tmβgly sample catalyzes transglycosylation reactions at
40 mM p-nitrophenyl β-glucoside, whereas only 40% is engaged in hydrolysis of this substrate. For Sfβgly the fraction
involved in transglycosylation is only 30 %. In addition, 48 % of a Tmβgly sample catalyzes transglycosylation reactions
at 8 mM methylumbelliferyl β-glucoside, whereas Sfβgly does not catalyze transglycosylation using this substrate. Interestingly,
these Tmβgly properties were grafted into Sfβgly by a single replacement of a residue forming a channel involved
in supplying the catalytic water molecules for attack on the covalent intermediate present in the reaction catalyzed
by β-glucosidases. Hence a single residue determines the ratio of hydrolysis to transglycosylation reactions catalyzed by
these β-glucosidases.
