Inactivation of human neutrophil elastase by 1,2,5-thiadiazolidin-3-one 1,1 dioxide-based sulfonamides

Abstract

The interaction of a series of 1,2,5-thiadiazolidin-3-one 1,1 dioxide-based sulfonamides with neutrophil-derived serine proteases was investigated. The nature of the amino acid component, believed to be oriented toward the S' subsites, had a profound effect on enzyme selectivity. This series of compounds were found to be potent, time-dependent inhibitors of human neutrophil elastase (HNE) and were devoid of any inhibitory activity toward neutrophil proteinase 3 (PR 3) and cathepsin G (Cat G). The results of these studies demonstrate that exploitation of differences in the S' subsites of HNE and PR 3 can lead to highly selective inhibitors of HNE.

Figure 1

Design and mechanism of action of inhibitor (I).

Figure 2

Progress curves for the inhibition of human neutrophil elastase (HNE) by inhibitor 4. Absorbance was monitored at 410 nm for reaction solutions containing 10 nM HNE, 105 μM MeOSuc-AAPV p-nitroanilide, 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 4 (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 Aliquots were withdrawn at different time intervals and assayed for enzymatic activity using MeOSuc-AAPV p-NA by monitoring the absorbance at 410 nm.

Figure 4

Time dependent loss of enzymatic activity. Percent remaining activity versus time plot obtained by incubating inhibitor 4 (0.125 mM) with bovine trypsin (5 μM) in 0.025 M phosphate buffer containing 0.1 M NaCl, pH 7.51, and 1% DMSO. Aliquots were withdrawn at different time intervals and assayed for enzymatic activity using N-(p-Tosyl)-Gly-Pro-Lys p-NA by monitoring the absorbance at 410 nm.

Scheme 1

Synthesis of inhibitors 4–11