Gene and properties of thermostable 4-alpha-glucanotransferase of Thermotoga neapolitana

Two clones that produced a thermostable enzyme hydrolyzing starch, amylose, and amylopectin were selected from a genome library of anaerobic extremely thermophilic bacterium Thermotoga neapolitana. The inserts of their recomb inant plasmids ware sequenced. Both plasmids had the mgtA gene for maltodex trin glycosyltransferase of 442 amino acid residues. The deduced molecular weight of the enzyme, 51.9 kDa, was confirmed by SDS-PAGE. Maltodextrin gly cosyltransferase (4-alpha-glucanotransferase) [EC 2.4.1.25] hydrolyzed the 1,4-alpha-glycoside bonds in oligomeric and polymeric 1,4-alpha-glucans and transferred oligosaccharides (maltotriose being the shortest one) to accep tor maltodextrins. The highest enzymic activity was observed at pH 7.0 and at 85 degrees C.