An exceptionally cold-adapted alpha-amylase from a metagenomic library of a cold and alkaline environment

A cold-active alpha-amylase, Amy(I3C6), identified by a functional metagenomics approach was expressed in Escherichia coli and purified to homogeneity. Sequence analysis showed that the Amy(I3C6) amylase was similar to alpha-amylases from the class Clostridia and revealed classical characteristics of cold-adapted enzymes, as did comparison of the kinetic parameters K (m) and k (cat) to a mesophilic alpha-amylase. Amy(I3C6) was shown to be heat-labile. Temperature optimum was at 10-15 A degrees C, and more than 70 % of the relative activity was retained at 1 A degrees C. The pH optimum of Amy(I3C6) was at pH 8-9, and the enzyme displayed activity in two commercial detergents tested, suggesting that the Amy(I3C6) alpha-amylase may be useful as a detergent enzyme in environmentally friendly, low-temperature laundry processes.