title: Catalytic versatility of trehalase: synthesis of alpha-D-glucopyranosyl alpha-D-xylopyranoside from beta-D-glucosyl fluoride and alpha-D-xylose.
abstract: Trehalase was previously shown (see ref. 5) to hydrolyze alpha-D-glucosyl fluoride, forming beta-D-glucose, and to synthesize alpha, alpha-trehalose from beta-D-glucosyl fluoride plus alpha-D-glucose. Present observations further define the enzyme's separate cosubstrate requirements in utilizing these nonglycosidic substrates. alpha-D-Glucopyranose and alpha-D-xylopyranose were found to be uniquely effective in enabling Trichoderma reesei trehalase to catalyze reactions with beta-D-glucosyl fluoride. As little as 0.2mM added alpha-D-glucose (0.4mM alpha-D-xylose) substantially increased the rate of enzymically catalyzed release of fluoride from 25mM beta-D-glucosyl fluoride at 0 degrees. Digests of beta-D-glucosyl fluoride plus alpha-D-xylose yielded the alpha, alpha-trehalose analog, alpha-D-glucopyranosyl alpha-D-xylopyranoside, as a transient (i.e., subsequently hydrolyzed) transfer-product. The need for an aldopyranose acceptor having an axial 1-OH group when beta-D-glucosyl fluoride is the donor, and for water when alpha-D-glucosyl fluoride is the substrate, indicates that the catalytic groups of trehalose have the flexibility to catalyze different stereochemical reactions.
mesh_terms: D004187:Disaccharides / Q000138:chemical synthesis*; D005947:Glucose / Q000031:analogs & derivatives; D007700:Kinetics; D009904:Optical Rotation; D013379:Substrate Specificity; D014198:Trehalase / Q000378:metabolism*; D014242:Trichoderma / Q000201:enzymology; D014994:Xylose
chemical_list: D004187:Disaccharides; C030364:glucosyl fluoride; C048281:alpha-glucopyranosyl alpha-xylopyranoside; D014994:Xylose; D014198:Trehalase; D005947:Glucose