Impact of binding mechanism on selective inhibition of histone deacetylase isoforms

Abstract

Industrialized drug screening campaigns usually deliver hundreds of compounds that are active on a particular pharmaceutical target. In the light of high failure rates of drug candidates due to unforeseeable off-target toxicity, the early identification of the most promising compounds with high potential for target selectivity is an urgent need to improve the quality of lead compounds and lower attrition rates in the drug development process. The reliable prediction of the selectivity of active substances for a target protein is a challenging task.

A comprehensive study of the binding kinetics, thermodynamics and selectivity of chemically related ligands of histone deacetylase (HDAC) like amidohydrolase from Pseudomonas aeruginosa (HDAH_pa) reveals one general binding mechanism for all analyzed compounds consisting of a preceding conformational selection step followed by an optional subsequent induced fit. Depending on the chemical structure the ligands bind to one or two of at least three protein conformations with different rate constants. Although these kinetic and mechanistic differences hamper the predictability of selectivity for the HDAC inhibitors, we demonstrate that the enthalpy weighted binding constant K_d^ΔHis a useful metric to predict isoform selectivity of inhibitors against HDAC enzymes and relatively robust toward different but related binding mechanisms.

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Depending on their chemical structures ligands recognize different conformers of histone deacetylase (HDAC) like amidohydrolase from P. aeruginosa and bind via a general mechanism consisting of chemical selection and induced fit. Although differences in binding kinetics and reaction pathway may hamper the predictability of selectivity for HDAC inhibitors, the enthalpy weighted binding constant K_d^ΔH proves to be a useful metric to predict isoform selectivity of inhibitors against HDAC enzymes, which is fairly robust toward different but related binding mechanisms.

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