Kubo Akiko, Arai Yuka, Nagashima Shigeyuki, Yoshikawa Takafumi
School of Pharmaceutical Sciences, Kitasato University, 5-9-1 Shirokane, Minato-ku, Tokyo, 108-8641, Japan.
Arch Biochem Biophys. 2004 Sep 15;429(2):198-203. doi: 10.1016/j.abb.2004.06.021.
In comparison with the amino acid sequences of seven species of glucosyltransferases and six species of galactosyltransferases, glutamine and histidine are highly conserved as the last amino acid residue of a glycosyltransferase-specific conserved region (UDPGT) in glucosyltransferases and galactosyltransferases, respectively. Consequently, the sugar donor specificities of glycosyltransferases are successfully altered by a single amino acid point mutation. UDP-galactose:anthocyanin galactosyltransferase (ACGaT), isolated from Aralia cordata, acquired glucosyltransferase activity in addition to the inherent galactosyltransferase activity by replacing histidine with glutamine. In contrast, UDP-glucose:flavonoid glucosyltransferase (UBGT), isolated from Scutellaria baicalensis, did not acquire galactosyltransferase activity by replacing glutamine with histidine, and exhibited a remarkable decrease in glucosyltransferase activity.
与七种葡萄糖基转移酶和六种半乳糖基转移酶的氨基酸序列相比，谷氨酰胺和组氨酸分别作为葡萄糖基转移酶和半乳糖基转移酶中糖基转移酶特异性保守区域（UDPGT）的最后一个氨基酸残基高度保守。因此，通过单个氨基酸点突变可成功改变糖基转移酶的糖供体特异性。从辽东楤木中分离出的UDP - 半乳糖：花青素半乳糖基转移酶（ACGaT），通过将组氨酸替换为谷氨酰胺，除了具有固有的半乳糖基转移酶活性外，还获得了葡萄糖基转移酶活性。相反，从黄芩中分离出的UDP - 葡萄糖：类黄酮葡萄糖基转移酶（UBGT），用组氨酸替换谷氨酰胺后未获得半乳糖基转移酶活性，且葡萄糖基转移酶活性显著降低。
