Elastase and

Elastase-like proteinases are serine proteinases that recognized peptide residues with linear aliphatic side chains (alanyl, valyl, leucyl or isoleucyl residues) and that effect hydrolysis of the polypeptide chain on the carboxy-terminal side of these residues. Examples of elastase-like proteinase are pancreatic elastase, neutrophil elastase and proteinase-3. 

There are other substrates for the E. coli Met(0) peptide reductase, one of which is Met(0)-a-l-PI. The native protein is the major serum elastase inhibitor that functions by forming a binary complex with elastase which inhibits its activity. Met(0)-a-l-PI, on the other hand, which can be formed by treatment of the protein with TV-chlorosuccinimide, cannot form a complex with elastase and therefore is not able to inhibit elastase activity117,118. Table 6 shows, however, that when Met(0)-a-l-PI is incubated in the presence of Met(0)-peptide reductase and dithiothreitol the protein regains its ability to form a complex with elastase and inhibit elastase activity119. Similar to results found with Met(0)-L12 reduced thioredoxin could replace the dithiothreitol as reductant in the enzymatic reaction. 

TABLE 7.1. Kinetic Parameters for the Hydrolysis of Different Peptides by Elastase and Chymotrypsin... 

Figure 50-6. Scheme illustrating (A) normal inactivation of elastase by a,-antitrypsin and (B) situation in which the amount of a,-antitrypsin is substantially reduced, resulting in proteolysis by elastase and leading to tissue damage. 

In inflammatory conditions, activated PMNs may pro-teolytically (by release of lysosomal enzymes) and oxidatively (by release of HOCl) inactivate ai-antitrypsin. Studies of synovial fluid samples from patients with RA showed that a i-antitrypsin was both cleaved and oxidized, resulting in inactivation (Chidwick et al., 1991, 1994). Free-radical attack on ai-antitrypsin and its subsequent inactivation may contribute to the destruction of joint tissues in arthritis due to the imbalance between elastase and its inhibitors. 

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... 

Proteinases and antiproteinases are part of the normal protective and repair mechanisms in the lungs. The imbalance of proteinase-antiproteinase activity in COPD is a result of either increased production or activity of destructive proteinases or inactivation or reduced production of protective antiproteinases. AAT (an antiproteinase) inhibits trypsin, elastase, and several other proteolytic enzymes. Deficiency of AAT results in unopposed proteinase activity, which promotes destruction of alveolar walls and lung parenchyma, leading to emphysema. 

Encompassing approx 6000 medicinal plant species, the medicinal flora of Asia and the Pacific comprise a fantastic source of pharmacologically active products, and the number of plant species principally used for the treatment of inflammation can be estimated to be more that 380. This chapter will focus on the potentials of medicinal plants of Asia as a source of original anti-inflammatory drugs, with particular interest payed to inhibitors of phospholipase A2, COX, lipoxygenases, elastase, and NOS. 

Cramer, E.M., Beesley, J.E., Pulford, K.A.F., Breton-Gorius, J., and Mason, D.Y. (1989) Colocalization of elastase and myeloperoxidase in human blood and bone marrow neutrophils using a monoclonal antibody and immunogold. Am. J. Pathol. 134, 1275-1284. 

In this method, ai-antiproteinase inhibits the hydrolytic enzyme elastase, and the remaining elastase activity is measured by monitoring increases in absorbance at410 nm. Martmez-Tome and others (2001) used a method based on this reaction to measure the antioxidant activity of broccoli amino acids and of Mediterranean spices. 

This is a 29-kDa protein that has NH 2-terminal sequence homology with elastase and cathepsin G. However, it contains glycine and not serine at the predicted catalytic site, and so lacks protease and peptidase activity. Purified azurocidin kills a range of organisms (e.g. E. coli, S.faecalis, and C. albicans) in vitro. It functions optimally at pH 5.5 and in conditions of low ionic strength. 

C5a is inactivated by the myeloperoxidase-H202 system, which oxidises a methionine residue (Met 70) on the molecule group A streptococcal endo-proteinases also abolish chemotactic activity of C5a and related compounds. Neutrophil lysosomal enzymes (e.g. elastase and cathepsin G) also destroy C5a chemotactic activity, but as these proteases are inhibited by the serum antiproteinases, a -antiproteinase and a2-macroglobulin, the physiological role of neutrophilic proteases in the inactivation of C5a is questionable. Two chemotactic factor inactivators have been found in human serum an a-globulin that specifically and irreversibly inactivates C5-derived chemotactic factors, and a / -globulin that inactivates bacterial chemotactic factors. These activities are heat labile (destroyed by treatment at 56 °C for 30 min) and are distinct from those attributable to anaphylatoxin inactivator. An apparently specific inhibitor of C5-derived chemotactic activity has also been described in human synovial fluid and peritoneal fluid. This factor (molecular mass of 40 kDa) is heat stable and acts directly on C5a. 

A. Janoff, Elastases and Emphysema. Current Assessment of the Protease-Antiprotease Hypothesis , Am. Rev. Respir. Dis. 1985, 132, 417-433. 

Adjacent half-cystine residues are present in many peptides and proteins. In most of the cases they form two disulfide bonds with other cysteines in the molecule, unless the peptide bond between them is cis (see Section 6.1.5.1 ).t40 41 Specific enzymes that cleave the Cys-Xaa bond have not yet been discovered, although there are a few reports of cleavage of the Cys-Cys bond by enzymes such as elastase and pepsinJ42-43 For peptides with Cys-Cys bonds the cleavage method in Section 6.1.6.2.4 is recommended. 

Clinical pharmacology Alpha-1 antitrypsin deficiency is a chronic, hereditary, usually fatal, autosomal recessive disorder in which a low concentration of alphai-proteinase inhibitor is associated with slowly progressive, severe, panacinar emphysema that most often manifests itself in the third to fourth decades of fife. The pathogenesis of development of emphysema in alpha-1 antitrypsin deficiency is believed to be due to a chronic biochemical imbalance between elastase and alphai-proteinase inhibitor (the principal inhibitor of neutrophil elastase), which is deficient in alpha-1 antitrypsin disease. As a result it is believed that alveolar structures are unprotected from chronic exposure to elastase released from a chronic low-level burden of neutrophils in the lower respiratory tract, resulting in progressive degradation... 

In the small intestine, proteases released by the pancreas as zymogens become active. Each has a different specificity for the amino acid R-groups adjacent to the susceptible peptide bond. Examples of these enzymes are trypsin, chymotrypsin, elastase, and car-boxypeptidase A and B. The resulting oligopeptides are cleaved by aminopeptidase found on the luminal surface of the intestine. Free amino acids and dipeptides are then absorbed by the intestinal epithelial cells. 

The digestive enzymes trypsin, chymotrypsin, elastase, and proteinase E are related serine proteases. All three are synthesized in the pancreas which secretes 5-10 g per day of proteins, mostly the inactive proenzymes (zymogens) of digestive enzymes.191,192... 

From study of peptides formed by partial hydrolysis of the 32P-labeled chymotrypsin, the sequence of amino acids surrounding the reactive serine was established and serine 195 was identified as the residue whose side chain hydroxyl group became phosphorylated. The same sequence Gly-Asp-Ser-Gly was soon discovered around reactive serine residues in trypsin, thrombin, elastase, and in the trypsin-like cocoonase used by silkmoths to escape from their cocoons.198 We know now that these are only a few of the enzymes in a very large family of serine proteases, most of which have related active site sequences.199 200 Among these are thrombin and other enzymes of the blood-clotting cascade (Fig. 12-17), proteases of lysosomes, and secreted proteases. 

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