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Discussion 22 Inhibitors and Drugs. Questions. Explain how an inhibitor of glutamine:fructose aminotransferase (GFAT) would affect glycosylation? From a mechanistic point of view, how can an alkaloid that inhibits a glycosidase also block a glycosyltransferase?
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Questions • Explain how an inhibitor of glutamine:fructose aminotransferase (GFAT) would affect glycosylation? • From a mechanistic point of view, how can an alkaloid that inhibits a glycosidase also block a glycosyltransferase? • Propose chemical modifications to make to galactose to create an inhibitor of sialyltransferases. • How would you go about obtaining an inhibitor of glycans that are initiated by the addition of O-fucose to EGF repeats in Notch? • Design a glycan-based therapeutic that acts by blocking the interaction of a naturally occurring glycan with glycan-binding proteins on an intact (or live) microbe. • Identify at least two enzymes that might be targets for designing inhibitors of selectin-mediated cell adhesion and propose a strategy for obtaining selective inhibitors. • How can an enzyme inhibitor also act as a chemical chaperone? • The binding affinity of hemagglutinin to monomeric sialic acid is very weak, with a Kd in the millimolar range. Explain how influenza virus manages to bind to host cells with very high avidity despite the weak affinity of its receptor for sialic acid. • A portion of erythropoietin (EPO) produced by CHO cells is not full sialylated (i.e., some glycoforms have exposed galactose residues on their N-glycans). What sugars might be added to the cell culture media to increase the overall level of EPO sialylation? • Explain how increasing the extent of glycosylation of recombinant glycoproteins can increase their half-life in vivo. • Describe the potential deleterious effects of producing recombinant therapeutic proteins in cultured animal cells of non-human origin.
50.3 GlcNAcstatin PUGNAc NAG-thiazoline
Figure 51.1. Examples of natural products possessing glycan components. Streptomycinand erythromycin are antibiotics, doxorubicin is an anti-cancer drug and digoxin is usedto treat cardiovascular disease.
Figure 51.2. The synthetic influenza neuraminidase inhibitors RelenzaTM and TamifluTM.
Figure 51.3. Glycomimetic E-selectin inhibitors based on sialyl Lewis X.