X‐ray crystallographic structural studies of α‐amylase I from Eisenia fetida. Issue 9 (2nd September 2020)

• Record Type: Journal Article
• Authors: Hirano, Yu; Tsukamoto, Kana; Ariki, Shingo; Naka, Yuki; Ueda, Mitsuhiro; Tamada, Taro
• Is Part Of: Acta crystallographica. Volume 76:Issue 9(2020)
• Page Start: 834
• Page End: 844
• Publication Date: 2020-09-02
• Subjects: amylase -- Eisenia fetida -- cold‐active enzymes -- substrate complex -- glycine‐rich loop -- substrate recognition -- structural flexibility; X-ray crystallography -- Periodicals; Crystallography -- Periodicals; Molecular biology -- Periodicals; Molecular structure -- Periodicals; Biomolecules -- Structure -- Periodicals; Cytology -- Periodicals; Biomolecules -- Structure; Crystallography; Cytology; Molecular biology; Molecular structure; X-ray crystallography; Periodicals; 548
• DOI: 10.1107/S2059798320010165
• Languages: English
• ISSNs: 2059-7983

Abstract

Abstract : X‐ray crystal structures were determined of the wild type and an inactive mutant of α‐amylase from the earthworm Eisenia fetida . Structural analyses reveal the molecular properties that are responsible for catalytic activity at low temperatures and substrate recognition. Abstract : 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 Ca 2+ ‐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.