Elastases

Human elastase-1 (EC 3.4.21.36 no systematic name El) is an anionic protease belonging to the family of serine proteases. It is a carboxyendopeptidase that catalyzes hydrolysis of native elastin, the major structural fibrous protein in connective tissue, with a special affinity for the carboxyl group of alanine, valine, and leucine. 

Historically, any proteinases that hydrolyze elastin have been named elastases. The genes coding for the elastases are clustered on chromosome 19, and three main types of enzymes are known (I) pancreatic El, (2) pancreatic elas-tase-2 (EC 3.4.21.71), and (3) pancreatic endopeptidase-3 (EC 3.4.21.70), also called cholesterol-binding proteinase.  

El measurement in stool is the most reliable and sensitive noninvasive procedure for the diagnosis of chronic pancreatic insufficiency. However, such a test does not consistently separate mild to moderate insufficiency cases from healthy controls (see Table 48-15). Unlike fecal CHY, El provides no information helpful to the therapeutic management of the patient. 

Methods for the Determination of Elastase-1 in Feces An ELISA method in a microplate sandwich format is commercially available to measure El mass concentrations in stool samples. 

The enzyme has been found to be stable in stool samples for up to 1 week at room temperature. 

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. 

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Bode, W., Papamokos, E., Musil, D. The high-resolution X-ray crystal structure of the complex formed between subtilisin Carlsberg and eglin c, an elastase inhibitor from the leech Hirudo medicinalis. Eur. J. Biochem. 166 (1987) 673-692... 

Pancrease Pancreatectomy Pancreatic a-amylase Pancreatic dornase Pancreatic elastase Pancreatic hypertrophy Pancreatic lipase Pancreatin [8049-47-6]... 

This is nicely illustrated by members of the chymotrypsin superfamily the enzymes chymotrypsin, trypsin, and elastase have very similar three-dimensional structures but different specificity. They preferentially cleave adjacent to bulky aromatic side chains, positively charged side chains, and small uncharged side chains, respectively. Three residues, numbers 189, 216, and 226, are responsible for these preferences (Figure 11.11). Residues 216... 

Figure 11.11 Schematic diagrams of the specificity pockets of chymotrypsin, trypsin and elastase, illustrating the preference for a side chain adjacent to the scisslle bond In polypeptide substrates. Chymotrypsin prefers aromatic side chains and trypsin prefers positively charged side chains that can interact with Asp 189 at the bottom of the specificity pocket. The pocket is blocked in elastase, which therefore prefers small uncharged side chains.

How would substrate preference be changed if the glycine residues in trypsin at positions 216 and 226 were changed to alanine rather than to the more bulky valine and threonine groups that are present in elastase This question was addressed by the groups of Charles Cralk, William Rutter, and Robert Fletterick in San Francisco, who have made and studied three such trypsin mutants one in which Ala is substituted for Gly at 216, one in which the same substitution is made at Gly 226, and a third containing both substitutions. 

Shotton, D.M., Watson, H.C. Three-dimensional structure of tosyl-elastase. Nature 225 811-816, 1970. 

Trypsin, chymotrypsin, and elastase all carry out the same reaction—the cleavage of a peptide chain—and although their structures and mechanisms are quite similar, they display very different specificities. Trypsin cleaves peptides... 

FIGURE 16.16 Comparison of the amino acid sequences of chymotrypsinogen, trypsino-gen, and elastase. Each circle represents one amino acid. Nmnbering is based on the sequence of chymotrypsinogen. Filled circles indicate residues that are identical in all three proteins. Disnlfide bonds are indicated in yellow. The positions of the three catalytically important active-site residues (His, Asp °-, and Ser ) are indicated. 

FIGURE 16.19 The substrate-binding pockets of trypsin, chymotrypsin, and elastase. 

Oxo-4//-pyrido[],2-n]pyrimidin-2-yl]oxymethylsaccharin derivatives 418 exhibited human leukocyta elastase inhibitory activities (94EUP626378, 95USP5378720). 2-Substituted 4//-pyrido[l, 2-n]pyrimidin-4-one (419) is a potent human leukocyta elastase inhibitors (A", 1.79/xM) (96USP5512576). The 4//-pyrido[l,2-n]pyrimidin-4-one moiety was included in leukotriene antagonist 2-ethynylthiazole derivatives (98JAP(K) 98/195063)... 

Figure 15.6 Chromatogram of a plasma standard of human leukocyte elastase inhibitors obtained by using LC-LC. Adapted from Journal of Liquid Chromatography and Related Technologies, 19, R. A. Earley and L. R Tini, Versatile multidimensional chromatographic system for di ug discovery as exemplified by the analysis of a non-peptidic inhibitor of human leukocyte elastase , pp. 2527-2540, 1996, by courtesy of Marcel DekkeiTnc.

One intensively investigated feature of the inflammatory process in COPD is the release of proteases from neutrophils and monocytic cells that destroy elastin and other components of the interstitial matrix (Table 1). The best studied protease is neutrophil elastase. Independent of its elastolytic activity, neutrophil elastase is a potent secretagogue. More recently matrix metalloproteases (MMP) have received increasing attention, in particular MMP 12 (macrophages elastase). To which extent and how exactly these proteases become activated is not clear at present. 

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. 

PA S1 S01.131 Neutrophil elastase Drug target for emphysema, cystic fibrosis, adult respiratory distress syndrome, rheumatoid arthritis and other diseases... 

PA S1 S01.153 Pancreatic elastase Drug target for acute pancreatitis... 

Elastase-like Proteinases Electrochemical Driving Force Electroencephalogram (EEG)... 

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