Wen You, Xu Jiahui, Pan Donglei, Wang Chenghua
College of Light Industry and Food Engineering, Guangxi University, Nanning 530004, People's Republic of China.
Food Chem X. 2023 Feb 4;17:100593. doi: 10.1016/j.fochx.2023.100593. eCollection 2023 Mar 30.
Xanthine oxidase is an oxidase that has a molybdopterin structure with substrate inhibition. Here, we show that a single point mutation (Q201) in the xanthine oxidase (AbXOD) obtained mutant Q201E ( =799.44 s, no inhibition) with high enzyme activity and decrease of substrate inhibition in 5 mmol/L high substrate model, and which cause two loops structure change at active center, characterized by complete loss of substrate inhibition without reduction of enzymatic activity. Molecular docking results showed that the change of flexible loop increased the affinity between substrate and enzyme, and the formation of a π-π bond and two hydrogen bonds made the substrate more stable in the active center. Ultimately, Q201E can still maintain better enzyme activity under high purine content (an approximately 7-fold improvement over the wild-type), indicating a broader application prospect in the manufacture of low-purine food.
黄嘌呤氧化酶是一种具有钼蝶呤结构且存在底物抑制作用的氧化酶。在此，我们表明，在黄嘌呤氧化酶（AbXOD）中一个单点突变（Q201）产生了突变体Q201E（kcat = 799.44 s，无抑制作用），其在5 mmol/L高底物模型中具有高酶活性且底物抑制作用降低，并且该突变导致活性中心的两个环结构发生变化，其特征是完全丧失底物抑制作用而酶活性未降低。分子对接结果表明，柔性环的变化增加了底物与酶之间的亲和力，并且形成的一个π-π键和两个氢键使底物在活性中心更稳定。最终，Q201E在高嘌呤含量下仍能保持较好的酶活性（比野生型提高约7倍），表明其在低嘌呤食品制造中具有更广阔的应用前景。
