Heterologous Over-expression ofα-1,6-Fucosyltransferase fromRhizobium sp.: Application to the Synthesis of the Trisaccharideβ-D-GlcNAc(1→4)- [α-L-Fuc-(1→6)]-D-GlcNAc, Study of the Acceptor Specificity and Evaluation of Polyhydroxylated Indolizidines as Inhibitors
作者:Agatha Bastida、Alfonso Fernández-Mayoralas、Ramón Gómez Arrayás、Fatima Iradier、Juan Carlos Carretero、Eduardo García-Junceda
DOI:10.1002/1521-3765(20010601)7:11<2390::aid-chem23900>3.0.co;2-0
日期:2001.6.1
An efficient heterologous expression system fur overproduction of the enzyme alpha -1,6-Fucosyltransferase (alpha -1,6-FucT) from Rhizobium sp, has been developed. The gene codifying for the alpha -1.6-FucT was amplified by PCR using specific primers. After purification, the gene was cloned in the plasmid pKK2233. The resulting plasmid, pKK1.6FucT, was transformed into the E. coli strain XL1-Blue MRF'. The protein was expressed both as inclusion bodies and in soluble form. Changing the induction time a five-fold increase of enzyme expressed in soluble form was obtained. In this way five units of enzyme alpha -1,6-FucT can be obtained per liter of culture. A crude preparation of the recombinant enzyme was used for the synthesis of the branched trisaccharide alpha -D-GlcNAc-(1 --> 4)-[alpha -L-Fuc-(1 --> 6)]-D-GlcNAc (3), from chitobiose (2) and GDP-Fucose (1). After purification, the trisaccharide 3 was obtained in a 84% overall yield. In order to elucidate the structural requirements for the acceptors, the specificity of the enzyme was studied towards mono-, di- and trisaccharides, which are structurally related to chitobiose. The enzyme uses, among others, the disaccharide N-acetyl lactosamine as a good substrate: the monosaccharide GlcNAc is a weak acceptor. Finally, several racemic polyhydroxylated indolizidines have been tested as potential inhibitors of the enzyme. Indolizidine 21 was the best inhibitor with an IC50 of 4.5 x 10(-5) M. Interestingly, this compound turned out to be the best mimic For the structural features of the fucose moiety in the presumed transition state.