Inhibition of Human Alcohol Dehydrogenases by Formamides

Abstract

Human alcohol dehydrogenase (HsADH) comprises class I (α, β, and γ), class II (π), and class IV (σ) enzymes. Selective inhibitors of the enzymes could be used to prevent the metabolism of alcohols that form toxic products. Formamides are unreactive analogues of aldehydes and bind to the enzyme−NADH complex [Ramaswamy, S.; Scholze, M.; Plapp, B. V. Biochemistry1997, 36, 3522−3527]. They are uncompetitive inhibitors against varied concentrations of alcohol, and this makes them effective even with saturating concentrations of alcohols. Molecular modeling led to the design and synthesis of a series of cyclic, linear, and disubstituted formamides. Evaluation of 23 compounds provided structure−function information and selective inhibitors for the enzymes, which have overlapping but differing substrate specificities. Monosubstituted formamides are good inhibitors of class I and II enzymes, and disubstituted formamides are selective for the α enzyme. Selective inhibitors, with K_i values at pH 7 and 25 °C of 0.33−0.74 μM, include N-cyclopentyl-N-cyclobutylformamide for HsADH α, N-benzylformamide for HsADH β₁, N-1-methylheptylformamide for HsADH γ₂, and N-heptylformamide for HsADH σ and HsADH β₁.