@article{oai:repo.qst.go.jp:00080542,
 author = {Hirano, Yuu and Tsukamoto, Kana and Ariki, Shingo and Naka, Yuki and Ueda, Mitsuhiro and Tamada, Taro and Yuu, Hirano and Taro, Tamada},
 journal = {Acta Crystallographica Section D},
 month = {Aug},
 note = {The earthworm Eisenia fetida has some 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 using wild type and the inactive E249Q mutant. Ef-Amy I has structural similarities to mammalian α-amylases, including porcine pancreatic and human pancreatic α-amylases. Structural comparisons between both the overall structures as well as the Ca2+ binding sites in Ef-Amy I and the mammalian α-amylases indicate that the Ef-Amy I has increased structural flexibility and more solvent-exposed acidic residues. These structural features in Ef-Amy I can contribute to the observed catalytic activities at low temperatures because many cold-adapted enzymes have similar structural properties. The structure of the substrate complex in the inactive mutant of Ef-Amy I shows that a maltohexaose molecule is bound at the active site and a maltotetraose is bound at the cleft between the N- and C-terminal domains. The recognition of substrate molecules in Ef-Amy I exhibits some differences from those observed in the structures of human pancreatic α-amylase. This result provides insights into the structural modulation of the recognition of substrates and inhibitors.},
 pages = {834--844},
 title = {X-ray crystallographic structural studies of α-amylase I from Eisenia fetida},
 volume = {76},
 year = {2020}
}