Purification and characterization of a new α-amylase of intermediate thermal stability from the yeast Lipomyces kononenkoae

A new alpha-amylase from the extracellular culture of the yeast Lipomyces kononenkoae CBS 5608 has been purified to homogeneity by ammonium sulphate treatment, affinity binding on cross-linked starch, and DEAE-Biogel A chromatography. The enzyme was monomeric, with an apparent M(r) of 76 kilodaltons, pI < 3.5, and optimum pH 4.5-5.0, and exhibited intermediate thermal stability. The temperature for optimal enzyme activity was 70 degrees C. It is a glycoprotein with both N- and O-linked sugars. Kinetic analyses indicate that the enzyme has an endoamylolytic mechanism. The kM for soluble starch was 0.80 g.L-1 and the kcat was 622.s-1.