New amylase (AmyKS) was purified from a newly isolated Bacillus subtilis US572 strain. The optimum pH and temperature recorded for enzyme activity were 6 and 60 °C, respectively. It displayed a marked thermostability with a half-life of 10 min at 70 °C. Amy is a Ca2+ independent enzyme and able to hydrolyze soluble starch into single sugars with predominant proportions of maltose and maltotriose. It presents a high affinity towards soluble starch with a Km value of 0.252 mg mL-1. The analysis of the enzyme in native and denaturing conditions suggests that it has a dimeric form (140 kDa). This is the first report on the purification and characterization of a nonmaltogenic Bacillus α-amylase with a dimeric structure. A 3D model and a dimeric model of AmyKS were constructed and accordingly evidence was found about the high substrate affinity and the high catalytic efficiency of this enzyme. A study was carried out with a newly isolated bacterial strain yielding extracellular amylase.
