Mechanism of inhibition of cathepsin K by potent, selective 1, 5-diacylcarbohydrazides: a new class of mechanism-based inhibitors of thiol proteases. Academic Article uri icon


  • The nature of the inhibition of thiol proteases by a new class of mechanism-based inhibitors, 1,5-diacylcarbohydrazides, is described. These potent, time-dependent, active-site spanning inhibitors include compounds that are selective for cathepsin K, a cysteine protease unique to osteoclasts. The 1,5-diacylcarbohydrazides are slow substrates for members of the papain superfamily with inhibition resulting from slow enzyme decarbamylation. Enzyme-catalyzed hydrolysis of 2,2'-N, N'-bis(benzyloxycarbonyl)-L- leucinylcarbohydrazide is accompanied by formation of a hydrazide-containing product and a carbamyl-enzyme intermediate that is sufficiently stable to be observed by mass spectrometry and NMR. Stopped-flow studies yield a saturation limited value of 43 s(-)(1) for the rate of cathepsin K acylation by 2,2'N, N'-bis(benzyloxycarbonyl)-L-leucinylcarbohydrazide. Inhibition potency varies among proteases tested as reflected by 2-3 orders of magnitude differences in K(i) and K(obs)/I, but all eventually form the same stable covalent intermediate. Reactivation rates are equivalent for all enzymes tested (1 x 10(-)(4) s(-)(1)), indicating hydrolysis of a common carbamyl-enzyme form. NMR spectroscopic studies with cathepsin K and 2,2'-N,N'-bis(benzyloxycarbonyl)-L-leucinylcarbohydrazide provide evidence of inhibitor cleavage to generate a covalent carbamyl-enzyme intermediate rather than a tetrahedral complex. The product Cbz-leu-hydrazide does not appear enzyme-bound after cleavage in the NMR spectra, suggesting that the stable inhibited form of the enzyme is the thioester complex. 1, 5-diacylcarbohydrazides represent a new class of unreactive cysteine protease inhibitors that share a common mechanism of action across members of the papain superfamily. Both S and S' subsite interactions are exploited in achieving high selectivity and potency.

published proceedings

  • Biochemistry

altmetric score

  • 3

author list (cited authors)

  • Bossard, M. J., Tomaszek, T. A., Levy, M. A., Ijames, C. F., Huddleston, M. J., Briand, J., ... Tew, D. G.

citation count

  • 33

complete list of authors

  • Bossard, MJ||Tomaszek, TA||Levy, MA||Ijames, CF||Huddleston, MJ||Briand, J||Thompson, S||Halpert, S||Veber, DF||Carr, SA||Meek, TD||Tew, DG

publication date

  • November 1999