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Publication Abstract from PubMed

The earthworm Eisenia fetida possesses several cold-active enzymes, including alpha-amylase, beta-glucanase and beta-mannanase. E. fetida possesses two isoforms of alpha-amylase (Ef-Amy I and II) to digest raw starch. Ef-Amy I retains its catalytic activity at temperatures below 10 degrees 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 alpha-amylases, including the porcine pancreatic and human pancreatic alpha-amylases. Structural comparisons of the overall structures as well as of the Ca(2+)-binding sites of Ef-Amy I and the mammalian alpha-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 alpha-amylase. This result provides insights into the structural modulation of the recognition of substrates and inhibitors.

X-ray crystallographic structural studies of alpha-amylase I from Eisenia fetida.,Hirano Y, Tsukamoto K, Ariki S, Naka Y, Ueda M, Tamada T Acta Crystallogr D Struct Biol. 2020 Sep 1;76(Pt 9):834-844. doi:, 10.1107/S2059798320010165. Epub 2020 Aug 25. PMID:32876059^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.