REACTION-MECHANISM OF A NEW GLYCOSYLTREHALOSE-PRODUCING ENZYME ISOLATED FROM THE HYPERTHERMOPHILIC ARCHAEUM, SULFOLOBUS-SOLFATARICUS KM1

An amylolytic activity, which converts soluble starch to alpha,alpha-t rehalose (trehalose), was found in the cell homogenate of the hyperthe rmophilic, acidophilic archaeum Sulfolobus solfataricus KM1. Two enzym es, a glycosyltransferase and an amylase, which are essential for this activity, were purified to homogeneity. A glycosyltransferase catalyz ed the conversion of maltooligosaccharides to glycosyltrehaloses. Base d on a detailed analysis of the reaction products, kinetic parameters, and an experiment using H-3-labeled substrates, it was verified that glycosyltransferase transferred an oligomer segment of maltooligosacch aride to the C1-OH position of glucose, located at the reducing end of the maltooligosaccharide, to produce a glycosyltrehalose having an al pha-1,1 linkage, The reaction appears to be intramolecular, Nine strai ns of the Sulfolobaceae family were found to have glycosyltransferases .