Novel Transglucosylating Reaction of Sucrose Phosphorylase to Carboxylic Compounds

Abstract

We screened for the carbohydrate-active enzymes that catalyze transglycosylation reactions on carboxylic compounds. Sucrose phosphorylase from Streptococcus mutans showed remarkable transglucosylating activity on benzoic acid, especially under acidic conditions. Sucrose phosphorylase from Leuconostoc mesenteroides also showed the activity, although it was very weak. Three main products were detected from the reaction mixture with sucrose, benzoic acid and S. mutans sucrose phosphorylase. These compounds were identified as 1-O-benzoyl α-D-glucopyranose, 2-O-benzoyl α-D-glucopyranose and 2-O-benzoyl β-D-glucopyranose on the basis of their isolation and the isolation of their acetylated products and subsequent spectroscopic analyses. Time-course analyses of the enzyme reaction and the degradation of 1-O-benzoyl α-D-glucopyranose proved that 1-O-benzoyl α-D-glucopyranose was initially produced by the transglucosylation reaction of the enzyme, and 2-O-benzoyl α-D-glucopyranose and 2-O-benzoyl β-D-glucopyranose were produced from 1-O-benzoyl α-D-glucopyranose by intramolecular acyl migration reaction. The acceptor specificity in the transglucosylation reaction of S. mutans sucrose phosphorylase was also examined. The enzyme could transglucosylate toward various carboxylic compounds. Comparison of the pH-dependence of transglucosylation activities of the enzyme on phosphate, hydroquinone and acetic acid suggest that an undissociated carboxylic group is essential as the acceptor molecule for the transglucosylation reaction on carboxylic compounds. We also obtained 1-O-acetyl α-D-glucopyranose using the transglucosylation reaction of the enzyme. The sensory test of acetic acid and the glucosides revealed that the sour taste of acetic acid was markedly reduced by glucosylation.