N-acetylglucosamine transferase (OGT) is an enzyme that binds N-acetylglucosamine (GlcNAc) to peptide residues of the hydroxyl group of amino acids serine and threonine through the oxygen atom by means of the sugar donor UDP-GlcNAc. This dynamic post-translation modification takes place on proteins in the nucleus, cytoplasm, and mitochondria. Even though GlcNAcylation is ostensibly a simple process that has a single binding enzyme (OGT) and a single enzyme for cleaving (N-acetylglucosaminidase, OGA) the GlcNAc molecule, however, it is very complex because it modifies over 1.000 proteins. The research in the field of the enzyme has been performed for over 30 years. Its excessive functioning is associated with numerous chronic and incurable diseases, such as diabetes, cancer, and Alzheimer's disease. Up until now, the OGT inhibitors are either toxic and unselective or inactive in vivo because they do not cross cell membranes. By fixing the compounds of the UDP binding pocket OGT we gained more hits with the quinolinone-4-carboxamide core. In the syntheses, therefore, we derived from 2-oxo-quinoline-4-carboxylic acid which, likely, imitates the binding of the uridine part of the UDP. We bound various amines to 2-oxo-quinoline-4-carboxylic acid by the coupling reactions with hydroxybenzotriazole (HOBt) and 1-ethyl-3-(3-dimethylaminopropyl)carboiimide (EDC) reagents with their purpose to bind in the ribose and diphosphate binding pocket of the enzyme. We synthesized 7 compounds and evaluated them with the in vitro test UDP-GloTM. The strongest inhibitors were compounds 4 and 7. The compounds inhibited the activity of the OGT enzyme at a concentration of 1 mM entirely. We can conclude that it is favorable for the successful binding on the enzyme that the enzyme has hydrogen bond acceptors and/or donors. Therefore, compound 7 served as a starting point for further synthesis. In this series of syntheses, we bound different fragments to the compound by forming the amide bond with the purpose to achieve even more interactions in the binding site. We sent the synthesized compounds to testing by the Transceener UDP method. The strongest inhibitors of the OGT activity were the compounds 11 which inhibits the enzyme-catalyzed reaction to a 95.0% range and 32 which inhibits the enzyme 82.1% by volume at a concentration of 0.5 µM. Synthesized compounds in the OGT binding site form numerous hydrogen bonds likely. However, they are poorly soluble in water. Therefore, further research will be necessary in order to achieve better efficiency.
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