Purification and Characterization of α‐Amylases of an Alkalopsychrotrophic Micrococcus sp

Two amylases of an alkalopsychrotrophic Micrococcus were purified by chromatographies of DEAE‐Toyopearl, Butyl‐Toyopearl and Shodex WS‐2003. Molecular weights and pI values of the purified enzymes, I and II, were 185000 and 125000 by SDS‐PAGE and 4.8 and 4.3 by isoelectric focusing, respectively. Enzyme I had not only amylase but also pullulanase activity. In the presence of Ca 2+ ions, other properties of both enzymes were very similar: optimum temperature 55–60°C, optimum pH 7.5–8.0 k m value for maltopentaose 0.09 mM. Both amylases were completely inactivated after incubation with EDTA at 30°C and thereafter, could be reactivated by an addition of CaCl 2 . In the absence of Ca 2+ ions, amylase I became thermoresistant, while the thermostability of amylase II decreased. Neither amylase activity of enzyme I nor enzyme II was inhibited by pullulan.