ACCEPTOR SPECIFICITY IN THE GLUCOSYLATION REACTION OF BACILLUS-SUBTILIS X-23 ALPHA-AMYLASE TOWARDS VARIOUS PHENOLIC-COMPOUNDS AND THE STRUCTURE OF KOJIC ACID GLUCOSIDE

The transglucosylating reaction of the alpha-amylase (HGE) from Bacill us subtilis X-23 was studied using various phenolic compounds, catechi ns, and kojic acid as acceptors. Among them, hydroquinone, resorcinol, catechol, catechins, and kojic acid were glucosylated with high effic iency by HGE. In glucosylating kojic acid, kojic acid monoglucoside wa s accumulated at the end of the reaction. Analysis of the structure of kojic acid glucoside by H-1-NMR and C-13-NMR indicated that glucose w as transferred to the hydroxymethyl group of kojic acid kojic acid and that the resultant compound was pyranosyl-alpha-O-2-methyl-5-hydroxy- gamma-pyrone. Comparing kojic acid and kojic acid glucoside, the solub ility of the glucoside was about ten times that of aglucone. In additi on, the stability of kojic acid was improved by glucosylation.