文摘
We describe a standardized approach for searching potent and selective inhibitors of glycosyltransferases by high throughput quantitative MALDI-TOFMS-based screening of focused compound libraries constructed by 1,3-dipolar cycloaddition of the desired azidosugar nucleotides with various alkynes. An aminooxy-functionalized reagent with a stable isotope was conjugated with oligosaccharides to afford glycopeptides as acceptor substrates with improved ion sensitivity. Enhanced ionization potency of new substrates allowed for MALDI-TOFMS-based facile and quantitative analysis of enzymatic glycosylation in the presence of glycosyl donor substrates. A non-natural synthetic sugar nucleotide was identified to be the first highly specific inhibitor for rat recombinant α2,3-(N)-sialyltransferase (α2,3ST, IC50 = 8.2 μM), while this compound was proved to become a favorable substrate for rat recombinant α2,6-(N)-sialyltransferase (α2,6ST, Km = 125 μM). Versatility of this strategy was demonstrated by identification of two selective inhibitors for human recombinant α1,3-fucosyltransferase V (α1,3-FucT, Ki = 293 nM) and α1,6-fucosyltransferase VIII (α1,6-FucT, Ki = 13.8 μM).