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

Sucrose conversion by sucrose isomerase from Protaminobacter rubrum, Serratia plymuthica and Erwinia rhapontici was investigated in the presence of different monosaccharides in the reaction mixture. These conditions led to inhibitory 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 sucrose molecule into the active site, and thereafter, to propose the possible biochemical reactions leading to the formation of different products from sucrose. This study also underlines the close homologies between these enzymes.