Synergistic inhibition of human alpha-1,3-fucosyltransferase V

Human alpha-1,3-fucosyltransferase V (FucT V), which catalyzes the transfer of L-fucose moiety from guanosine diphosphate beta-L-fucose (GDP-Fuc) to an acceptor sugar To form sialyl Lewis x (sLe(x)), was shown to proceed through an ordered, sequential mechanism by product inhibition studies. The designed azatrisaccharide propyl 2-acetamido-2-deoxy-4-O-(beta-D-galactopyranosyl)-3 -O-(2-(N-(beta-L-homofuconojirimycinyl))ethyl)-alpha-D- glucopyranoside (2), prepared by covalently linking the N-group of beta-L-homofuconojirimycin (1) to the 3-OH of LacNAc through an ethylene unit, in the presence of GDP was found to be an effective inhibitor of FucT V. In the presence of 30 mu M GDP, the concentration of 2 necessary to cause 50% inhibition was reduced 77-fold to 31 mu M. Presumably, the azatrisaccharide and GDP form a complex which mimics the transition state of the enzymatic reaction. Given the low affinity of FucT V for its substrate LacNAc (K-m = 35 mM), the designed azatrisaccharide in the presence of GDP represents the most potent synergistic inhibitor complex reported so far.