Molecular cloning, expression and characterization of alpha-amylase gene from a marine bacterium Pseudoalteromonas sp. MY-1.

A gene (amyA) encoding an extracellular alpha-amylase from a marine bacterium Pseudoalteromnonas sp. MY-1 was cloned and expressed in Escherichia coli. It comprised an open-reading-frame of 2,007 base pairs and encoded a protein of 669 amino acids with a predicted molecular weight of 73,770 daltons and a pI of 5.15. The entire amino acid sequence of amyA gene showed 86% similarity to the alpha-amylase preproprotein from Pseudoalteromonas haloplanktis. It consisted of a signal peptide, alpha-amylase catalytic domain and an amy C domain. The recombinant amylase was purified to homogeneity and biochemically characterized. The enzyme revealed maximum activity at pH 7.0 and 40 degrees C. The enzyme hydrolyzed soluble starch and some maltooligosaccharides to several oligosaccharides, and maltose was the common product from different substrates.