α-Anomer-selective glucosylation of (+)-catechin by the crude enzyme, showing glucosyl transfer activity, of Xanthomonas campestris WU-9701 |
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Authors: | Toshiyuki Sato Hiroyuki Nakagawa Jun Kurosu Keishiro Yoshida Takanori Tsugane Susumu Shimura Kohtaro Kirimura Kuniki Kino Shoji Usami |
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Affiliation: | a Department of Applied Chemistry, School of Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan;b Central Laboratory, Lotte Co. Ltd., 3-1-1 Numakage, Urawa, Saitama 336-0027, Japan |
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Abstract: | 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-Na2HPO4 buffer (pH 6.5) containing 1.2 M maltose at 45°C, only one (+)-catechin glucoside was selectively obtained as a product. The (+)-catechin glucoside was identified as (+)-catechin 3′-O-α-
-glucopyranoside (α-C-G) by 13C-NMR, 1H-NMR and two-dimensional HMBC analysis. The reaction at 45°C 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°C, 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. |
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Keywords: | anomer-selective glucosylation (+)-catechin glucoside transglucosylation Xanthomonas campestris |
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