Structural and Functional Basis of Difructose Anhydride III Hydrolase, Which Sequentially Converts Inulin Using the Same Catalytic Residue,ACS Catalysis

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Structural and Functional Basis of Difructose Anhydride III Hydrolase, Which Sequentially Converts Inulin Using the Same Catalytic Residue
ACS Catalysis ( IF 11.3 ) Pub Date : 2018-10-11 00:00:00 , DOI: 10.1021/acscatal.8b02424
Shuhuai Yu ₁ , Hui Shen ₂ , Yuanyuan Cheng ₁ , Yingying Zhu ₁ , Xu Li ₂ , Wanmeng Mu _{1,

3}

Affiliation

Fructan inulin is composed of polymeric fructoses linked by O-glycosidic bonds, and a variety of enzymes are involved in its decomposition to provide energy for organisms. Specifically, inulin fructotransferase (IFTase) depolymerizes inulin to difructose anhydride III (DFA-III). DFA-III was reported to be further degraded by DFA-III hydrolyase (DFA-IIIase). This work reveals that the structure of DFA-IIIase is a trimer, with each monomer displaying a right-handed β-helix fold, which resembles IFTase except for an extra lid covering the active center. With this lid, DFA-IIIase is capable of converting inulin to DFA-III (IFTase activity) in addition to hydrolyzing DFA-III using the same site and reaction conditions. This unusual and unexpected sequential catalysis is ascribed to the extremely conserved residues in the active center of IFTase and DFA-IIIase and the protonated states of the catalytic residue that are regulated by the opening and closing of the lid. This work paves the way for further investigation of the metabolism of inulin in nature and provides an example of sequential enzymatic catalysis.

中文翻译：

双果糖酐III水解酶的结构和功能基础，使用相同的催化残基依次转化菊粉

果糖菊粉由通过O-糖苷键连接的多聚果糖组成，并且多种酶参与其分解以为生物体提供能量。具体而言，菊粉果糖转移酶（IFTase）将菊粉解聚为果糖酐III（DFA-III）。据报道DFA-III被DFA-III水解酶（DFA-IIIase）进一步降解。这项工作揭示了DFA-IIIase的结构是三聚体，每个单体均表现出右旋β-螺旋折叠，与IFTase相似，只是一个额外的盖子覆盖了活性中心。有了这个盖子，除了使用相同的位点和反应条件水解DFA-III外，DFA-IIIase还能将菊粉转化为DFA-III（IFTase活性）。这种异常和出乎意料的顺序催化作用是由于IFTase和DFA-IIIase的活性中心中极为保守的残基以及由盖子的打开和关闭所调节的催化残基的质子化状态。这项工作为进一步研究自然界中的菊粉代谢铺平了道路，并提供了顺序酶催化的实例。

更新日期：2018-10-11

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