Download MendeleyX-ray crystallographic structural studies of alpha-amylase I from Eisenia fetida.
Hirano, Y., Tsukamoto, K., Ariki, S., Naka, Y., Ueda, M., Tamada, T.(2020) Acta Crystallogr D Struct Biol 76: 834-844
- PubMed: 32876059
- DOI: https://doi.org/10.1107/S2059798320010165
- Primary Citation of Related Structures:
6M4K, 6M4L, 6M4M - PubMed 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.
Organizational Affiliation:
Institute for Quantum Life Science, National Institutes for Quantum and Radiological Science and Technology, 2-4 Shirakata, Tokai, Ibaraki 319-1106, Japan.
