Abstract
We identified the raw-starch-digesting α-amylase genes a earthworm Eisenia fetid α amylase I and II (Ef-Amy I and Ef-Amy II). Each gene consists of 1,530 base pairs (bp) that encode proteins of 510 amino acids, as indicated by the corresponding mRNA sequences. Ef-Amy I and II showed an 89% amino acid identity. The amino acid sequences of Ef-Amy I and II were similar to those of the α-amylases from porcine pancreas, human pancreas, Tenebrio molitor, Oryctolagus cuniculus, and Xenopus (Silurana) tropicalis. Each gene encoding mature Ef-Amy I and II was expressed in the GS115 strain of Pichia pastoris. The molecular masses of the recombinant Ef-Amy I and II were 57 kDa each, and catalytically important residues of α-amylases of the GH family 13 were conserved in both proteins. These amylases exhibited raw-starch-digesting activity at 4 °C. The substrate specificities of rEf-Amy I and II were dissimilar. rEf-Amy I and II were shown to be active even in 40% ethanol, 4 M NaCl, and 4 M KCl.
Highlights
Earthworms can be found all over the world, especially in temperate and tropical regions, where there is plenty of moisture in the ground
We reported that Ef-Amy I was expressed in P. pastoris [8]
The present study shows that Ef-Amy II is functionally expressed in the earthworm species E. fetida
Summary
Earthworms can be found all over the world, especially in temperate and tropical regions, where there is plenty of moisture in the ground. Earthworms are divided into 23 families with over 700 genera and more than 7000 species. We found activities of glycoside hydrolases (GHs), such as cellulase, amylase, mannanase, and chitinase, in the crude enzyme so lution of Eisenia fetida [2,3,4,5]. To hydrolyze carbohydrates such as cel lulose, starch, mannan, and chitin, the earthworm secretes digestive juices to the intestinal tract. The endo-β− 1,4-glucanase, mannanase, and α-amylases from
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