Substrate and inhibitor studies on proteinase 3

Abstract

Various amino acid and peptide thioesters were tested as substrates for human proteinase 3 and the best substrate is Boc‐Ala‐Ala‐Nva‐SBzl with a k _cal/K _m value of 1.0 × 10⁶nM^it‐1s^it‐1 Boc‐Ala‐Ala‐AA‐SBzl (AA = Val, Ala, or Met) are also good substrates with k _cal/K _m values of (1‐4) × 10⁵ M⁻¹ s⁻¹. Substituted isocoumarins are potent inhibitors of proteinase 3 and the best inhibitors are 7‐amino‐4‐chloro‐3‐(2‐bromoethoxy)isocoumarin and 3.4‐dichloroisocoumarin (DCI) with k _obs/[I] values of 4700 and 2600 M⁻¹ s⁻¹, respectively. Substituted isocoumarins. peptide phosphonates and chloromethyl ketones inhibited proteinase 3 less potently than human neutrophil elastase (HNE) by 1‐2 orders of magnitude.