Cloning, purification and characterization of a thermostable amylosucrase from Deinococcus geothermalis

Amylosucrase is a transglucosidase that catalyses the synthesis of an amylose-type polymer from sucrose, an abundant agro-resource. Here we describe a novel thermostable amylosucrase from the moderate thermophile Deinococcus geothermalis (DGAS). The dgas gene was cloned and expressed in Escherichia coli. The encoded enzyme was purified and characterized. DGAS displays a specific activity of 44 U mg(-1), an optimal temperature of 50 degrees C and a half-life of 26 h at 50 degrees C. Moreover, it produces an alpha-glucan at 50 degrees C, with an average degree of polymerization of 45 and a polymerization yield of 76%. DGAS is thus the most active and thermostable amylosucrase known to date.