This amylase is a highly liquefying-type: oligomers appeared at the beginning of incubation, followed by a graded decrease in the amounts of maltotriose, maltose and glucose in prolonged incubation. Endohydrolysis of (1->4)-alpha-D-glucosidic linkages in polysaccharides containing three or more (1->4)-alpha-linked D-glucose units. Optimum pH is 5.5. Stable above pH 5.5. Optimum temperature is about 90 degrees Celsius. Highly thermostable. Retains 70% of its maximal activity after heating 1 hour at 90 degrees Celsius, but no decrease in activity was observed within the same time at 80 degrees Celsius. Belongs to the glycosyl hydrolase 57 family.