Hirade Yoshihiro, Kotoku Naoyuki, Terasaka Kazuyoshi, Saijo-Hamano Yumiko, Fukumoto Akemi, Mizukami Hajime
Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamada-oka, Suita City, Osaka 565-0871, Japan.
Graduate School of Pharmaceutical Sciences, Osaka University, 1-6 Yamada-oka, Suita City, Osaka 565-0871, Japan.
FEBS Lett. 2015 Jul 8;589(15):1778-86. doi: 10.1016/j.febslet.2015.05.010. Epub 2015 May 12.
C-Glucosyltransferase is an enzyme that mediates carbon-carbon bond formation to generate C-glucoside metabolites. Although it has been identified in several plant species, the catalytic amino acid residues required for C-glucosylation activity remain obscure. Here, we identified a 2-hydroxyflavanone C-glucosyltransferase (UGT708D1) in soybean. We found that three residues, His20, Asp85, and Arg292, of UGT708D1 were located at the predicted active site and evolutionarily conserved. The substitution of Asp85 or Arg292 with alanine destroyed C-glucosyltransferase activity, whereas the substitution of His20 with alanine abolished C-glucosyltransferase activity but enabled O-glucosyltransferase activity. The catalytic mechanism is discussed on the basis of the findings.
C-葡萄糖基转移酶是一种介导碳-碳键形成以生成C-葡萄糖苷代谢物的酶。尽管它已在多种植物物种中被鉴定出来，但C-糖基化活性所需的催化氨基酸残基仍不清楚。在这里，我们在大豆中鉴定出一种2-羟基黄酮C-葡萄糖基转移酶（UGT708D1）。我们发现UGT708D1的三个残基His20、Asp85和Arg292位于预测的活性位点且在进化上保守。用丙氨酸取代Asp85或Arg292会破坏C-葡萄糖基转移酶活性，而用丙氨酸取代His20会消除C-葡萄糖基转移酶活性，但会使O-葡萄糖基转移酶活性得以实现。基于这些发现对催化机制进行了讨论。
