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Inhibition of Mandelate Racemase by Boron-Based Inhibitors: Different Binding Modes for Benzoxaboroles Versus Boronic
Joshua A Hayden1, Anika Jabin2, Oliver P Kuehm1
1Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada.
Mandelate racemase (MR) enzyme activity can be inhibited by various boronic acid derivatives. Structure-activity studies reveal potent inhibition by naphthyl-, furan-, and thiophene-boronic acids, and benzoxaboroles like tavaborole.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Structural biology
Background:
- Mandelate racemase (MR) is a model enzyme for studying the deprotonation of carbon acid substrates.
- Boronic acids are known inhibitors of enzymes that catalyze deprotonation reactions.
Purpose of the Study:
- To conduct a detailed structure-activity relationship study of boronic acid derivatives as competitive inhibitors of Mandelate Racemase (MR).
- To investigate the binding modes and inhibitory potential of various aryl boronic acids and benzoxaboroles.
Main Methods:
- Enzyme inhibition assays to determine inhibition constants (Ki).
- Structure-activity relationship analysis of diverse boronic acid derivatives.
- X-ray crystallography and 11B NMR spectroscopy to elucidate binding interactions.
Main Results:
- 2-Naphthylboronic acid, furan-3-boronic acid, and thiophene-3-boronic acid exhibited potent inhibition (Ki values in the low μM range).
- Chlorine substitution on pyridine or pyrimidine rings enhanced inhibitory potency.
- Benzoxaboroles, including tavaborole, were identified as potent competitive inhibitors.
- Structural analysis revealed distinct binding modes for aryl boronic acids (His 297 interaction) and benzoxaboroles (Lys 166 interaction).
Conclusions:
- Boronic acid derivatives, particularly substituted aryl boronic acids and benzoxaboroles, are effective competitive inhibitors of Mandelate Racemase.
- The binding mode of inhibitors significantly influences their inhibitory potency.
- This study provides insights into the rational design of enzyme inhibitors targeting carbon acid-dependent enzymes.
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