Glycosylation of anthocyanins by glycosyltransferases

研究了从紫玉米色素中大量制备的半纯色素和纯花青素3-葡萄糖苷（C3 G）与各种糖底物在各种糖相关酶催化下的转糖基化反应，结果表明环糊精葡聚糖转移酶（CGTases）最适合生成糖基化C3 G（Gly-C3 Gs）。接下来，在作为最佳酶的商业CGTase Contizyme下，用商业α-环糊精粉末Dexypearl K-100作为最佳糖底物进行C3 G的转糖基化。确定了最佳糖浓度为100 g/100 mL，最佳pH值为4.0，最佳色素浓度为1 g/100 mL，最佳反应时间为3 h，在此条件下进行大规模糖基化反应，可得到大量高度糖基化的亲水性Gly-C3 Gs。其中，6个主要的Gly-C3 Gs（G1-G6）可以通过各种柱分离和纯化。通过HPLC、UV-Vis和ESI/TOFMS分析，推测G1-G6为非天然型糖苷，在C3 G-3-葡萄糖残基的4-OH上通过α-1，4键依次糖苷化葡萄糖链，因此，我们可以通过与小规模试验相同的方法进行大规模反应，得到预期的Gly-C3 Gs，但每个分离的糖苷量非常少。因此，产率的条件检验和稳定性和功能性的评价是未来的课题。

The semi-purified pigment and the pure cyanidin 3-glucoside (C3G) prepared in large quantities from purple corn pigment were examined the transglycosylation with various sugar substrates catalyzed by various sugar-related enzymes, resulting that cyclodextrin glucanotransferases (CGTases) best generated glycosylated C3G (Gly-C3Gs). Next, the transglycosylation of C3G was conducted with a commercial α-cyclodextrin powder Dexypearl K-100 as an optimum sugar substrate under a commercial CGTase Contizyme of as an optimum enzyme. It was ascertained that the optimum sugar concentration 100 g/100 mL, the optimum pH 4.0, the optimum pigment concentration 1g/100mL, and optimum reaction time 3 hours.Under the optimum reaction condition, the large-scale glycosylation gave many highly glycosylated and hydrophilic Gly-C3Gs. Of them, six major Gly-C3Gs (G1-G6) could be isolated through various column separation and purification. HPLC, UV-Vis, and ESI/TOFMS analyses of the isolated G1-G6 resulted that they were presumed the non-natural type polyglycosides sequentially glycosidated glucose chain with α-1,4 bond on 4-OH of C3G-3-glucosyl residue.Thus, we could obtain Gly-C3Gs expected by the large-scale reaction advanced in the same way as small-scale test, but each isolated glycoside was in very small amount. Therefore, conditional examination for yield up and evaluation for the stability and the functionality are future topics.