Uridine-5¢-diphospho-1-a-D-glucose (UDP-Glc) is a common substrate used by glucosyltransferases, including certain bacterial toxins such as Toxins A and B from Clostridium difficile. Fluorescent analogs of UDP-Glc have been prepared for use in our studies of the clostridial toxins. These compounds are related to the methylanthraniloylATP compounds commonly used to probe the chemistry of ATP-dependent enzymes. The reaction of excess methylisatoic anhydride with UDP-Glc in aqueous solution yields primarily the 2¢ and 3¢ isomers of methylanthraniloyl-UDPGlc (MUG). As the 2¢ and 3¢ isomers readily interconvert, this isomeric mixture was copurified by HPLC away from the other isomeric products, and was characterized.
