Effects of structure on inhibitory activity in a series of mechanism-based inhibitors of human neutrophil elastase

Abstract

A structurally-diverse series of carboxylate derivatives based on the 1,2,5-thiadiazolidin-one 1,1 dioxide scaffold were synthesized and used to probe the S' subsites of human neutrophil elastase (HNE) and neutrophil proteinase 3 (Pr 3). Several compounds are potent inhibitors of HNE but devoid of inhibitory activity toward Pr 3, suggesting that the S' subsites of HNE exhibit significant plasticity and can, unlike Pr 3, tolerate various large hydrophobic groups. The results provide a promising framework for the design of highly selective inhibitors of the two enzymes.

Figure 1

Mechanism of action of inhibitor (I).

Figure 2

Progress curves for the inhibition of human neutrophil elastase (HNE) by inhibitor 18. Absorbance was monitored at 410 nm for reaction solutions containing 10 nM HNE, MeOSuc-AAPV p-nitroanilide (105 μM), and the inhibitor at the indicated inhibitor to enzyme ratios in 0.1 M HEPES buffer containing 0.5 M NaCl, pH 7.25, and 2.5% DMSO. The temperature was maintained at 25 °C and reactions were initiated by the addition of enzyme.

Figure 3

Time dependent loss of enzymatic activity. Percent remaining activity versus time plot obtained by incubating inhibitor 17 or 18 (7 μM) with human neutrophil elastase (700 nM) in 0.1 M HEPES buffer containing 0.5 M NaCl, pH 7.25, and 1% DMSO. Aliquots were withdrawn at different time intervals and assayed for enzymatic activity using MeOSuc-AAPV p-NA by monitoring the absorbance at 410 nm.

Scheme 1

Synthesis of inhibitor (I) Reagents and conditions: a) ClSO₂N=C=O/t-BuOH/TEA; b) TFA; c) NaH/DMF; d) PhSCH₂Cl/TEA; e) NaH/DMF then methyl iodide or benzyl bromide; f) SO₂Cl₂; g) NaI/acetone then R₃ COOH/DBU/CH₂CI₂