Characterization of the maltooligosyl trehalose synthase from the thermophilic archaeon Sulfolobus acidocaldarius

We report the molecular characterization and the detailed study of the reco mbinant maltooligosyl trehalose synthase mechanism from the thermoacidophil ic archaeon Sulfolobus acidocaldarius. The mts gene encoding a maltooligosy l trehalose synthase was overexpressed in Escherichia coli using the T7-exp ression system. The purified recombinant enzyme exhibited optimum activity at 75 degreesC and pH 5 with citrate-phosphate buffer and retained 60% of r esidual activity after 72 h of incubation at 80 degreesC. The recombinant e nzyme was active on maltooligosaccharides such as maltotriose, maltotetraos e, maltopentaose and maltoheptaose. Investigation of the enzyme action on m altooligosaccharides has brought much insight into the reaction mechanism. Results obtained from thin-layer chromatography suggested a possible mechan ism of action for maltooligosyl trehalose synthase: the enzyme, after conve rting the alpha -1,4-glucosidic linkage to an alpha -1,1-glucosidic linkage at the reducing end of maltooligosaccharide glc(n) is able to release gluc ose and maltooligosaccharide glc(n-1) residues. And then, the intramolecula r transglycosylation and the hydrolytic reaction continue, with the maltool igosaccharide glc(n-1) until the initial maltooligosaccharide is reduced to maltose. An hypothetical mechanism of maltooligosyl trehalose synthase act ing on maltooligosaccharide is proposed. (C) 2001 Federation of European Mi crobiological Societies. Published by Elsevier Science B.V. All rights rese rved.