Inhibition of UDP-GlcNAc:Galα1-3GalNAc-R (GlcNAc to GalNAc) β6-N-acetylglucosaminyltransferase from acute myeloid leukemia cells by photoreactive nitrophenyl substrate derivatives

Cells from patients with acute myeloid leukaemia (AML) contain an abnormally high UDP-GlcNAc:Galβ1-3Ga1NAc-R (GlcNAc to GalNAc) β6-N-acetylglucosaminyltransferase (core 2 β6-Gn-T) activity. Upon UV irradiation at 350 nm, the substrate Galβ1-3GalNAcα-p-nitrophenyl acted as an effective inhibitor for this enzyme but not for several other transferases. Preincubation with Galβ1-3GalNAcα-benzyl but not GalNAcα-benzyl protected core 2 β6-Gn-T from inhibition indicating that the inhibitor is specific for the substrate binding site of core 2 β6-Gn-T. A number of other nitrophenyl-sugar derivatives similarly acted as inhibitors for core 2 β6-Gn-T. GalNAcα-pnp at higher concernrations also inactivated UDP-Gal: GalNAc-R β3-galactosyltransferase from rat liver and AML cells and inhibition could be reduced by substrate protection. These results suggest that pnp-sugar derivatives may prove useful as specific inhibitors of glycosyltransferases and as affmity labels.