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X-ray crystallographic structural studies of α-amylase I from Eisenia fetida.
Acta Crystallographica Section D ( IF 2.6 ) Pub Date : 2020-09-02 , DOI: 10.1107/s2059798320010165 Yu Hirano 1 , Kana Tsukamoto 2 , Shingo Ariki 2 , Yuki Naka 2 , Mitsuhiro Ueda 2 , Taro Tamada 1
Acta Crystallographica Section D ( IF 2.6 ) Pub Date : 2020-09-02 , DOI: 10.1107/s2059798320010165 Yu Hirano 1 , Kana Tsukamoto 2 , Shingo Ariki 2 , Yuki Naka 2 , Mitsuhiro Ueda 2 , Taro Tamada 1
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The earthworm Eisenia fetida possesses several cold‐active enzymes, including α‐amylase, β‐glucanase and β‐mannanase. E. fetida possesses two isoforms of α‐amylase (Ef‐Amy I and II) to digest raw starch. Ef‐Amy I retains its catalytic activity at temperatures below 10°C. To identify the molecular properties of Ef‐Amy I, X‐ray crystal structures were determined of the wild type and of the inactive E249Q mutant. Ef‐Amy I has structural similarities to mammalian α‐amylases, including the porcine pancreatic and human pancreatic α‐amylases. Structural comparisons of the overall structures as well as of the Ca2+‐binding sites of Ef‐Amy I and the mammalian α‐amylases indicate that Ef‐Amy I has increased structural flexibility and more solvent‐exposed acidic residues. These structural features of Ef‐Amy I may contribute to its observed catalytic activity at low temperatures, as many cold‐adapted enzymes have similar structural properties. The structure of the substrate complex of the inactive mutant of Ef‐Amy I shows that a maltohexaose molecule is bound in the active site and a maltotetraose molecule is bound in the cleft between the N‐ and C‐terminal domains. The recognition of substrate molecules by Ef‐Amy I exhibits some differences from that observed in structures of human pancreatic α‐amylase. This result provides insights into the structural modulation of the recognition of substrates and inhibitors.
中文翻译：
Eetnia fetida的α-淀粉酶I的X射线晶体学结构研究。
蚯蚓蚯蚓具有几个冷活性酶，包括α淀粉酶，β葡聚糖酶和β-甘露聚糖酶。f。fetida具有两种亚型的α-淀粉酶（Ef-Amy I和II）来消化生淀粉。Ef-Amy I在低于10°C的温度下仍保持催化活性。为了确定Ef-Amy I的分子特性，确定了野生型和非活性E249Q突变体的X射线晶体结构。Ef-Amy I与哺乳动物的α-淀粉酶（包括猪胰和人的胰腺α-淀粉酶）在结构上相似。整体结构以及Ca 2+的结构比较Ef-Amy I和哺乳动物α-淀粉酶的结合位点表明Ef-Amy I具有增强的结构柔性和更多的溶剂暴露酸性残基。Ef-Amy I的这些结构特征可能有助于其在低温下观察到的催化活性，因为许多冷适应的酶具有相似的结构特性。Ef-Amy I失活突变体的底物复合物结构表明，麦芽六糖分子结合在活性位点上，麦芽四糖分子结合在N-和C-末端结构域之间的缝隙中。Ef-Amy I对底物分子的识别与人类胰腺α-淀粉酶的结构所观察到的有所不同。该结果提供了对底物和抑制剂识别的结构调节的见解。
更新日期：2020-09-02
中文翻译：
Eetnia fetida的α-淀粉酶I的X射线晶体学结构研究。
蚯蚓蚯蚓具有几个冷活性酶，包括α淀粉酶，β葡聚糖酶和β-甘露聚糖酶。f。fetida具有两种亚型的α-淀粉酶（Ef-Amy I和II）来消化生淀粉。Ef-Amy I在低于10°C的温度下仍保持催化活性。为了确定Ef-Amy I的分子特性，确定了野生型和非活性E249Q突变体的X射线晶体结构。Ef-Amy I与哺乳动物的α-淀粉酶（包括猪胰和人的胰腺α-淀粉酶）在结构上相似。整体结构以及Ca 2+的结构比较Ef-Amy I和哺乳动物α-淀粉酶的结合位点表明Ef-Amy I具有增强的结构柔性和更多的溶剂暴露酸性残基。Ef-Amy I的这些结构特征可能有助于其在低温下观察到的催化活性，因为许多冷适应的酶具有相似的结构特性。Ef-Amy I失活突变体的底物复合物结构表明，麦芽六糖分子结合在活性位点上，麦芽四糖分子结合在N-和C-末端结构域之间的缝隙中。Ef-Amy I对底物分子的识别与人类胰腺α-淀粉酶的结构所观察到的有所不同。该结果提供了对底物和抑制剂识别的结构调节的见解。
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