RESUMEN
Vibrio spp. play a vital role in the recycling of chitin in oceans, but several Vibrio strains are highly infectious to aquatic animals and humans. These bacteria require chitin for growth; thus, potent inhibitors of chitin-degrading enzymes could serve as candidate drugs against Vibrio infections. This study examined NAG-thiazoline (NGT)-mediated inhibition of a recombinantly expressed GH20 ß-N-acetylglucosaminidase, namely VhGlcNAcase from Vibrio campbellii (formerly V. harveyi) ATCC BAA-1116. NGT strongly inhibited VhGlcNAcase with an IC50 of 11.9 ± 1.0 µm and Ki 62 ± 3 µm, respectively. NGT was also found to completely inhibit the growth of V. campbellii strain 650 with an minimal inhibitory concentration value of 0.5 µm. ITC data analysis showed direct binding of NGT to VhGlcNAcase with a Kd of 32 ± 1.2 µm. The observed ΔG°binding of -7.56 kcal·mol-1 is the result of a large negative enthalpy change and a small positive entropic compensation, suggesting that NGT binding is enthalpy-driven. The structural complex shows that NGT fully occupies the substrate-binding pocket of VhGlcNAcase and makes an exclusive hydrogen bond network, as well as hydrophobic interactions with the conserved residues around the -1 subsite. Our results strongly suggest that NGT could serve as an excellent scaffold for further development of antimicrobial agents against Vibrio infections. DATABASE: Structural data are available in PDB database under the accession number 6K35.
Asunto(s)
Acetilglucosamina/análogos & derivados , Acetilglucosaminidasa/antagonistas & inhibidores , Proteínas Bacterianas/antagonistas & inhibidores , Tiazoles/farmacología , Vibrio/enzimología , Acetilglucosamina/química , Acetilglucosamina/farmacología , Acetilglucosaminidasa/química , Acetilglucosaminidasa/metabolismo , Animales , Infecciones Bacterianas/microbiología , Infecciones Bacterianas/prevención & control , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Dominio Catalítico , Cristalografía por Rayos X , Humanos , Concentración 50 Inhibidora , Cinética , Modelos Moleculares , Oligosacáridos/metabolismo , Dominios Proteicos , Especificidad por Sustrato , Termodinámica , Tiazoles/química , Vibrio/efectos de los fármacos , Vibrio/genética , Vibrio/crecimiento & desarrolloRESUMEN
ß-N-acetylglucosaminidases (GlcNAcases) play a crucial role in the metabolism of glycan-conjugated proteins/lipids in humans. Elevated levels of serum GlcNAcases have been associated with certain types of cancer, and GlcNAcases therefore serve as drug targets. Here, we employed virtual screening to identify two novel GlcNAcase inhibitors from the National Cancer Institute (NCI) Drug Library using a bacterial GH-20 GlcNAcase (VhGlcNAcase) as a search model. NSC73735 was shown to be most potent with IC50 of 12.7⯱â¯1.2⯵M, agreeing with Kd of 0.94⯱â¯0.2⯵M obtained by ITC. Molecular docking refinement indicated that Trp582 the key residue that interacted with all the inhibitor molecules. Docking NSC7373 into the active site of human O-GlcNAcase (hOGA) yielded reasonably good fit with the estimated Kd of 44.7⯵M, indicating its possibility to be a true binding partner. NSC73735 was shown to significantly suppress both cell growth and GlcNAcase activity of five cancer cell lines (U937, THP-1, MCF-7, HepG2 and PC-3) that express endogenous GlcNAcases. The cell cytotoxicity assay indicated the inherent effects of the lead compound on GlcNAcase expression with cancer cell proliferation, and therefore this novel GlcNAcase inhibitor may serve as a virtuous candidate for further development of highly potent anti-tumor agents.