Characteristics of alpha‐Amylase K, a Novel Amylase from a Strain of Bacillus subtilis

Abstract α‐Amylase K is a novel thermostable α‐amylase from Bacillus subtilis which produces maltohexaose from starch. Various methods showed the existance of two forms which did not differ significantly in action and which may therefore be isoenzymes. α‐Amylase K is stable at 60°C in the presence of additional calcium chloride with 80% activity remaining after 6d. It is completely deactivated after 10 min at 90°C and inhibited by tris‐(hydroxymethyl)‐aminomethane above pH 5.0. The purified α‐amylase K fractions are less thermostable than the original enzyme solution. α‐Amylase K is stable to freeze drying but reconstituted enzyme solution was less active at at pH‐values below of 5.8.