The stereochemical course of the reaction mechanism of trehalose phosphorylase from Schizophyllum commune

Phosphorolysis of alpha,alpha-trehalose catalyzed by trehalose phosphorylas e from the basidiomycete Schizophyllum commune proceeds via net retention o f anomeric configuration and yields alpha-D-glucose l-phosphate and alpha-D -glucose as the products. In reverse reaction, only the alpha-anomers: of D -glucose 1-phosphate and ID-glucose are utilized as glucosyl donor and acce ptor, respectively, and give exclusively the alpha,alpha-product. Trehalose phosphorylase converts alpha-D-glucose 1-fluoride and phosphate into alpha -D-glucose l-phosphate, a reaction requiring the stereospecific protonation of the glucosyl fluoride by a Bronsted acid. The results are discussed wit h regard to a plausible reaction mechanism of fungal trehalose phosphorylas e, (C) 1998 Federation of European Biochemical Societies.