Human leukocyte elastase inhibition

Le-Barillec K, Si-Tahar M, Balloy V, Chignard M. Proteolysis of monocyte CD14 by human leukocyte elastase inhibits lipopolysaccharide-mediated cell activation. J Clin Invest 1999 103 1039. 

Irreversible inhibition is probably due to the alkylation of a histidine residue.43 Chymotrypsin is selectively inactivated with no or poor inhibition of human leukocyte elastase (HLE) with a major difference the inactivation of HLE is transient.42,43 The calculated intrinsic reactivity of the coumarin derivatives, using a model of a nucleophilic reaction between the ligand and the methanol-water pair, indicates that the inhibitor potency cannot be explained solely by differences in the reactivity of the lactonic carbonyl group toward the nucleophilic attack 43 Studies on pyridyl esters of 6-(chloromethyl)-2-oxo-2//-1 -benzopyran-3-carboxylic acid (5 and 6, Fig. 11.5) and related structures having various substituents at the 6-position (7, Fig. 11.5) revealed that compounds 5 and 6 are powerful inhibitors of human leukocyte elastase and a-chymotrypsin thrombin is inhibited in some cases whereas trypsin is not inhibited.21... 

TABLE 11.1 Inhibition of a-Chymotrypsin and Human Leukocyte Elastase by Phenolic Esters of 6-(Chloromethyl)-2-oxo-2H-l-Benzopyran-3-Carboxylic Acid42... 

TABLE 11.2 Inhibition of Human Leukocyte Elastase, a-Chymotrypsin and Thrombin by 5 -Chloropyrid-3 -yl Derivatives at pH 8.0 and 25°C21... 

The acyl-enzyme can eliminate the 4-chlorine atom to generate this reactive intermediate that can then react with a nearby nucleophile such as His57 to give an alkylated acyl-enzyme derivative in which the inhibitor moiety is bound to the enzyme by two covalent bonds (Scheme 11.5). Inhibition is irreversible.59 The mechanism has been confirmed by X-ray structural analysis of protease-isocoumarin complexes. There is a cross-link between the inhibitor and the Serl95 and His57 residues of PPE.60 Human leukocyte elastase is also very efficiently inactivated.61... 

In addition to the aforementioned allenic steroids, prostaglandins, amino acids and nucleoside analogs, a number of other functionalized allenes have been employed (albeit with limited success) in enzyme inhibition (Scheme 18.56) [154-159]. Thus, the 7-vinylidenecephalosporin 164 and related allenes did not show the expected activity as inhibitors of human leukocyte elastase, but a weak inhibition of porcine pancreas elastase [156], Similarly disappointing were the immunosuppressive activity of the allenic mycophenolic acid derivative 165 [157] and the inhibition of 12-lipoxygenase by the carboxylic acid 166 [158]. In contrast, the carboxyallenyl phosphate 167 turned out to be a potent inhibitor of phosphoenolpyruvate carboxylase and pyruvate kinase [159]. Hydrolysis of this allenic phosphate probably leads to 2-oxobut-3-enoate, which then undergoes an irreversible Michael addition with suitable nucleophilic side chains of the enzyme. 

FR901277 - cyclic peptide that inhibits human leukocyte elastase... 

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. 

CONSENSUS SEQUENCES FOR HUMAN PANCREATIC SECRETORY TRYPSIN INHIBITOR (PSTI) VARIANTS, SELECTED BY PHAGE DISPLAY IN THE pSKAN8 VECTOR, WHICH INHIBIT EITHER BOVINE CHYMOTRYPSIN (CHY) OR HUMAN LEUKOCYTE ELASTASE (HLE) WITH SUBNANOMOLAR K, VALUES (REF. 72 AND P. ROTTGEN AND J. COLLINS, UNPUBLISHED DATA)... 

The reactive site of i-PI has a Ala-Ile-Pro-Met Ser-Ile-Pro-Pro sequence where the asterisk indicates the bond cleaved when i-PI pro-tase complexes are dissociated at high pH or by using nucleophiles. We have synthesized a number of peptides with the amino acid sequence at the ai-PI reactive site and have shown them to be perfectly adequate substrates for human leukocyte elastase. However, oxidation of the methionine residue of the substrates to a methionine sulfoxide residue (see Table III) almost completely destroys their reactivity toward human leukocyte elastase and other proteases (8,9). Oxidation of ai-PI itself destroys its ability to inhibit most proteases (10). 

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. 

Sulfonyl Fluorides. Sulfonyl fluorides inhibit serine proteases by reacting with the active-site serine residue. Previously we investigated the rates of inhibition of human leukocyte elastase and cathepsin G by a variety of sulfonyl fluorides and found relatively little selectivity or reactivity (38). However, we have discovered recently that the introduction of fluoroacyl groups into the sulfonyl fluoride structure gives considerable reactivity and selectivity for elastase (39). 

Doherty JB, et al. Cephalosporin antibiotics can be modified to inhibit human leukocyte elastase. Nature 1986 322 192-194. 

Q.-L. Ying and S. R. Simon. Kinetics of the inhibition of human leukocyte elastase by elafin, a 6-kilodalton elastase-specific inhibitor from human skin. Biochemistry 32 1866(1993). 

Several 9-(phosphonoalkyl)- and 9-(difluoroalkyl)-guanine derivatives (12, X = H or F) have been studied as potential inhibitors of guanylate kinase. The most pronounced effect was observed with n - 5 Phenoxymethylene bisphosphonates (13, where R R and R represent a variety of substituents) were prepared and found to act as inositol phosphatase inhibitors and antimanic agents some inhibited the enzyme with IC50 < 50 pmol 4-(Phosphonomethylphenoxy)-l-carbamoylazetidine-2-ones (14) inhibited human leukocyte elastase for 14 (R R = OEt = 1.2 x 10 moL s (ref. 38). 

An alternative therapy for anaphylactic shock and asthma is represented by tibenelast (64) which is orally effective by a poorly defined mechanism of action <90LS917>. A later study showed (64) to be a selective phosphodiesterase inhibitor <90MI 212-06>. Elastase inhibition also has potential in the treatment of insufficient lung function MR 889 (65) is an inhibitor of human leukocyte elastase and may have therapeutic utility for pulmonary emphysema <89BBR(I65)568>. Neltenexine (66) has recently been approved for the treatment of cystic fibrosis. 

L. AntonilU, E. ParoU, Role of the oligosaccharide inner core in the inhibition of human leukocyte elastase by chondroitin sulfates, Int. J. CUn. Pharmacol. Res. 13 (Suppl.) (1993) 11-17. 

N. Volpi, Inhibition of human leukocyte elastase activity by chondroitin sulfates, Chem. Biol. Interact. 105 (3) (1997) 157-167. 

Boje K, Lechtenberg M, Nahrstedt A (2003) New and known iridoid- and phenylethanoid glycosides from Harpagophytum procumbens and their in vitro inhibition of human leukocyte elastase. Planta Med 69 820-825... 

Full kinetic characterization for mechanism-based inhibition can be a challenge. Not only are there multiple rates to determine, but the mechanism of inhibition is often a combination of several different steps. The dividing line between alternate substrate inhibitors and the more eom-plex suicide inhibitors is often blurred, with some alternate substrates being virtually irreversible and some suicide substrates with high partition ratios and a significant alternate substrate element of inhibition. The following examples describe the characterization of an alternate substrate inhibitor and a suicide inhibitor of the serine protease human leukocyte elastase. 

A series of ynenol lactones (stmcture 2) were studied as inhibitors of human leukocyte elastase (Tam et al., 1984 Spencer et al., 1986 Copp et al., 1987). Some of the compounds were alternate substrate inhibitors, being hydrolyzed by the enzyme to the reactive I but then deacylat-ing without an inactivation step. However, with the compound 3-benzyl ynenol butyrolactone (stmcture 2, where R = benzyl, R = H), the acyl-enzyme (E-I ) was stable enough to allow the second alkylation step, resulting in inactivated enzyme. All kinetic constants were determined. Continuous assays gave biphasic kinetics, the second minor phase possibly due to the presence of isozymes or enantiomers of the inhibitor. Immediate diffusion-limited inhibition was observed and gave a competitive Ki value of 4.3 0.7 xM. The first phase of inhibition was saturable, and analysis of the rates gave = 0.090 0.007 s , and... 

The inhibition of human leukocyte elastase by the ynenol lactone was irreversible in the presence of the nucleophiles )6-mercaptoethanol and hydroxylamine and after size exclusion chromatography. The partition ratio r was evaluated in two different ways. Titration of the enzyme by suicide substrate using the plot shown in Fig. 13.3 gave r = 1.7 0.5. The partition ratio was also determined from the ratio of rates 3/ 4= 1.5. 

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