Tetrafluorination of Sugars as Strategy for Enhancing Protein–Carbohydrate Affinity: Application to UDP‐Galp Mutase Inhibition

Abstract

Tetrafluorinated analogues of both UDP-galactopyranose and UDP-galactofuranose have been synthesized and assayed against UDP-galactopyranose mutase, a key enzyme for Mycobacterium tuberculosis cell wall biosynthesis. Competition assays and STD-NMR spectroscopy techniques have evidenced not only the first unambiguous case of affinity enhancement through local sugar polyfluorination, but also showed that tetrafluorination can still have a beneficial effect on binding when monofluorination at the same position does not.

Structural Basis of Ligand Binding to UDP-Galactopyranose Mutase from Mycobacterium tuberculosis Using Substrate and Tetrafluorinated Substrate Analogues

“…N'Go et al 37 have reported that UDP-F 4 -Galf 4 adopts a high energy conformation ( 4 E) in its MtUGM-bound state, as evidenced by a H1-H4 nOe crosspeak obtained by a TRNOESY experiment, as opposed to the minimum energy conformation adopted in the free state ( 3 T 2 ). This in solution NMR-based observation is now confirmed by the X-ray crystallographic data obtained in this study.…”

The synthesis of tetrafluorinated aminosugars

“…[13] A successful inhibitor of the mycobacterial enzyme UDP-Gal mutase, based on a tetrafluorinated galactofuranose sugar, has been recently reported. [14] Figure 1. Tetrafluorinated sugars with the proposed aminosugar analogues.…”

Combined molecular dynamics, STD-NMR, and CORCEMA protocol yields structural model for a UDP-galactopyranose mutase–inhibitor complex

“…However, most of the UGM inhibitors developed to date have only moderate binding affinities in the micromolar range, [9][10][11][12][13][14][15][16][17][18] unsuitable for clinical application. Hence, understanding their bound geometries could be critical to improving the potency of UGM inhibitors.…”

“…One such micromolar inhibitor, UDP-(2,3-dideoxy)-2,2,3,3-tetrafluoro-D-galactofuranose (UDP-F4-Galf) (Scheme 1), has been recently developed and shows a K d of 53 lM against the model UGM enzyme from Klebsiella pneumoniae. 18 In addition, its binding epitope in complex with UGM has been mapped by saturation transfer difference (STD) NMR spectroscopy. 18 To reveal the bioactive bound conformation of this tetrafluorinated substrate analogue within the active site, we employ herein molecular dynamics (MD) simulations to construct its binding model with reduced (catalytically active) UGM.…”

“…18 In addition, its binding epitope in complex with UGM has been mapped by saturation transfer difference (STD) NMR spectroscopy. 18 To reveal the bioactive bound conformation of this tetrafluorinated substrate analogue within the active site, we employ herein molecular dynamics (MD) simulations to construct its binding model with reduced (catalytically active) UGM. This model is subsequently validated by quantitative comparisons between experimental STD effects and theoretical STD values calculated via complete relaxation and conformational exchange matrix (CORCEMA) analysis.…”