α-Anomer-Selective Glucosylation of (+)-Catechin by the Crude Enzyme, Showing Glucosyl Transfer Activity, of Xanthomonas campestris WU-9701

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α-Anomer-selective glucosylation of (+)-catechin was carried out using the crude enzyme, showing α-glucose transferring activity, of Xanthomonas campestris WU-9701 with maltose as a glucosyl donor. When 60 mg of (+)-catechin and 50 mg of the enzyme (5.25 units as maltose hydrolysing activity) were incubated in 10 ml of 10 mM citrate-Na_2HPO_4 buffer(pH6.5) containing 1.2 M maltose at 45℃, only one (+)-catechin glucoside was selectively obtained as a product. The (+)-catechin glucoside was identified as (+)-catechin 3′-O-α-D-glucopyranoside(α-C-G) by ^<13>C-NMR, ^1H-NMR and two-dimensional HMBC analysis. The reaction at 45℃ for 36 h under the optimum conditions gave 12 mM α-C-G, 5.4 mg/ml in the reaction mixture, and the maximum molar conversion yield based on the amount of (+)-catechin supplied reached 57.1%. At 20℃, the solubility in pure water of α-C-G, of 450 mg/ml, was approximately 100 fold higher than that of (+)-catechin, of 4.6 mg/ml. Since α-C-G has no bitter taste and a slight sweet taste compared with (+)-catechin which has a very bitter taste, α-C-G may be a desirable additive for foods, particularly sweet foods.
社団法人日本生物工学会の論文
2000-12-25