Synthesis of a fluorescent acceptor substrate for glycosyltransferases involved in the assembly of O-antigens of enterohemorrhagic Escherichia coli O157 and O5

The assembly of the repeating units of O-antigens in Gram negative bacteria is catalyzed by specific glycosyltransferases. Previously we used GlcNAc/GalNAcα-diphosphate-phenoxyundecyl as natural acceptor substrate analogs in assays of the transfer of radioactive sugars by bacterial glycosyltransferases. In order to develop new, fluorescence based assays we have synthesized a fluorescent acceptor P1-[11-(anthracen-9-ylmethoxy)undecyl]-P2-(2-acetamido-2-deoxy-α-d-galactopyranosyl) diphosphate and have shown that the compound was an excellent acceptor for glucosyltransferase WbdN from Escherichia coli (E. coli) O157 and for galactosyltransferase WbwC from E. coli O5. This is the first report of the Gal-transferase activity of the wbwC gene product of E.coli O5. The presence of the fluorescent label in the acceptor molecule allows the detection of glycosyltransferase reaction products with high sensitivity, eliminating the need for radioactive nucleotide sugars.

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► Fluorescent lipid diphosphate sugar.
► WbwC and WbdN substrate.
► Fluorescent assays.