Broadening the biocatalytic properties of recombinant sucrose synthase 1 from potato (Solanum tuberosum L.) by expression in Escherichia coli and Saccharomyces cerevisiae

The present paper describes the modification of the biochemical and biocatalytic characteristics of the recombinant glycosyltransferase sucrose synthase 1 (SuSy1, EC 2.4.1.13) from Solanum tuberosum L by expression in different hosts. SuSy1 catalyses the reversible conversion of sucrose and UDP to form UDP-alpha-D-glucose and D-fructose. Recombinant SuSy1 expressed in Saccharomyces cerevisiae was extensively characterized in our former studies. In contrast, the expression of SuSy1 in Escherichia coli resulted in striking differences concerning the biochemical and biocatalytic properties. The monosaccharides D-ribulose, D-tagatose, L-glucose, and L-rhamnose were identified as new acceptor substrates. Analysis of the phosphorylation status of recombinant yeast-SuSy1 and the yeast-SuSy1/S11A mutant by Fe3+-IMAC clearly demonstrated that the wild-type enzyme is phosphorylated at the conserved phosphorylation site S11 identified in all plant sucrose synthase enzymes. The mutant enzymes, yeast-SuSy1/S11A and E coli-SuSy1/S11 D, show also an altered spectrum of specific monosaccharides as acceptor substrates. This is the first report on broadening the biocatalytic potential of sucrose synthase by expression in different hosts and furthermore by mutation of a conserved phosphorylation site. We also demonstrate for the first time that recombinant SuSy1 is phosphorylated at the conserved serine 11 when expressed in S. cerevisiae. (C) 2008 Elsevier Inc. All rights reserved.