Purification and characterization of novel raw-starch-digesting and cold-adapted α-amylases from Eisenia foetida

Novel raw-starch-digesting and cold-adapted α-amylases (Amy I and Amy II) from the earthworm Eisenia foetida were purified to electrophoretically homogeneous states. The molecular weights of both purified enzymes were estimated to be 60,000 by SDS-PAGE. The enzymes were most active at pH 5.5 and 50 °C and stable at pH 7.0–9.0 and 50–60 °C. Both Amy I and II exhibited activities at 10 °C. The enzymes were inhibited by metal ions Cu2+, Fe2+, and Hg2+, and hydrolyzed raw starch into glucose, maltose and maltotriose as end products.