Bisubstrate Uridine-Mimetic-Peptide Conjugates As O-GlcNAc Transferase (OGT) Inhibitors

O-linked beta-N-acetylglucosamine transferase (OGT) is the pivotal mammalian enzyme that serves as a nutrient sensor, linking metabolic status to diverse cellular signalling pathways by catalyzing N-acetylglucosamine transfer to various proteins and detects fluctuations in UDP-GlcNAc concentrations. Increased UDP-GlcNAc levels induce O-GlcNAcylation of proteins, influencing the stability and localization of biomolecules, including transcription factors, kinases, phosphatases, tumour suppressors, and histone-modifying proteins. Dysregulation and excessive OGT expression can adversely impact cellular processes. The lack of potent and selective inhibitors for OGT has impeded the progress in understanding the enzyme and its molecular mechanisms. This research article details the successful development and synthesis of a series of bisubstrate analogue inhibitors, specifically focusing on inhibiting the O-GlcNAc transferase (OGT) enzyme. Compound 29 emerged as a promising inhibitor, demonstrating an IC50 value of 134.40 mu M in in-vitro assays. The study emphasizes the crucial role of the acceptor substrate analogue in bisubstrate inhibitor design, highlighting its equal importance alongside the donor substrate analogue. While donor substrate mimetics alone exhibited limited inhibition, their conjugation with appropriate peptides significantly enhanced the overall potency of the final bisubstrate inhibitor. Particularly, peptide derivatives proved superior as acceptor substrate analogues compared to normal substrate peptides. Preliminary data suggest the potential of uridine-mimetics, like Q6S and Q4 C, following scaffold structure refinement. In-silico predictions propose that replacing pyrophosphate with a flexible linker substantially improves physicochemical properties relevant to cell permeation. This comprehensive investigation offers valuable insights into designing and optimizing bisubstrate analogue inhibitors for OGT, revealing potential avenues for further refinement and development.