Proposition for the biochemical mechanism occurring in the sucrose isomerase active site

Sucrose conversion by sucrose isomerase from Protaminobacter rubrum, Serrat ia plymuthica and Erwinia rhapontici was investigated in the presence of di fferent monosaccharides in the reaction mixture. These conditions led to in hibitory effects and to glucosyl transfer of the glucose moiety of sucrose to the exogen monosaccharide. Comparison of the structure of the different inhibitors and acceptors has allowed us to suppose the binding of the sucro se molecule into the active site, and thereafter, to propose the possible b iochemical reactions leading to the formation of different products from su crose, This study also underlines the close homologies between these enzyme s. (C) 1998 Federation of European Biochemical Societies.