A thermostable maltose-tolerant alpha-amylase from Aspergillus tamarii.

An homogeneous fraction of alpha-amylase from Aspergillus tamarii was obtained by means of a very easy purification procedure. The enzyme is a glycoprotein containing 32% saccharide and MW of 37.5 kDa. Optimal of pH and temperature with starch as substrate were 4.5-6.5 and 50-55 degrees C. The enzyme was stable for several hours at temperature up to 65 degrees C. Starch, amylose, and amylopectin were the substrates preferentially hydrolysed and maltose and maltotriose were the main end products. The values of K(M) and V(max) for starch were 2 g/l and 880 micromoles reducing sugars/min.mg of protein, respectively. The purified enzyme was remarkably insensitive to end product inhibition, being only slightly inhibited by maltose and glucose up to 1.0 M.