Chloromethyl ketones , elastase

Peptide chloromethyl ketone inhibitors have been developed for almost every serine protease that has been characterized adequately (30). For example, human leukocyte elastase, due to its involvement in emphysema, has been studied extensively with this class of inhibitor (32). The rate at which peptide chloromethyl ketones inhibit elastase is influenced by their interaction with the primary substrate binding site (Si) of the enzyme and by interactions at other subsites. The most effective chloromethyl ketone elastase inhibitor found thus far is MeO-Suc-Ala-Ala-Pro-ValCH2Cl (MeO-Suc- = CH3OCOCH2CH2CO-). This will not inhibit the other major leukocyte protease, cathepsin G (see Table VI). In contrast, Z-Gly-Leu-Phe-CH2C1 (Z = C6H5CH2OCO-) inhibits cathepsin G, but not elastase. Both enzymes can be inhibited with Ac-Ala-Ala-Pr o-V alCH2Cl. 

Figure 4. Chloromethyl ketone elastase inhibitor attached to a HAM.

A was supported by a 3D X-ray structure of the inhibitor at the closely related porcine elastase (Navia, 1987) (Figure 13.12). After initially reversible inhibition (Figure 13.12, top two rows), time-dependent irreversible inhibition through covalent bonding of the dihydrothiazine ring of the inhibitor to the His-57 residue of the active site of the enzyme increasingly takes over (Figure 13.12, bottom row). Peptidyl chloromethyl ketones, known unspecific inhibitors, act in similar fashion. 

Powers, J. C., et al. 1977. Specificity of porcine pancreatic elastase, human leukocyte elastase and cathepsin G. Inhibition with peptide chloromethyl ketones. Biochim Biophys Acta 485 156. 

C. P. Dom, and K. Hoogsteen. Structure of human neutrophil elastase in complex with a peptide chloromethyl ketone inhibitor at 1.84 A resolution. Proc. Natl. Sci. USA 86 7 (1989). 

Two representative procedures are presented in detail. The first, preparation of Z-Gly-Leu-PheCH-Cl, involves deblocking of Z-PheCH-Cl and subsequent coupling of the deblocked chloromethyl ketone with Z-Gly-Leu-OH. This compound is an excellent inhibitor of chymotryp-sin and cathepsin G. The second procedure, that for Ac-Ala-Ala-Pro- ValCH-Cl, illustrates the synthesis of a peptide chloromethyl ketone from Boc-Val-OH with a minimum of isolation and purification along the way this compound is an excellent inhibitor of porcine pancreatic and human leukocyte elastase. ... 

Figure 3. Neutrophil elastase in chronic wound fluids is capable of degrading peptide growth factors. FTransforming growth factor- j was incubated alone (lane 1), with purified neutrophil elastase (lanes 2 and 3), and with 100 xg of chronic wound fluid (lanes 4 and 5) at 3TC for 90 minutes. The presence of intact growth factor was assessed by gel electrophoresis and autoradiography. A specific inhibitor of neutrophil elastase (10 xM N-methoxysuccinyl-ala-ala-pro-val-chloromethyl ketone) was included in lanes 3 and 5.

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