Elastases action

Unfortunately, the size of the crystallographic problem presented by elastase coupled with the relatively short lifedme of the acyl-enzyme indicated that higher resolution X-ray data would be difficult to obtain without use of much lower temperatures or multidetector techniques to increase the rate of data acquisition. However, it was observed that the acyl-enzyme stability was a consequence of the known kinetic parameters for elastase action on ester substrates. Hydrolysis of esters by the enzyme involves both the formation and breakdown of the covalent intermediate, and even in alcohol-water mixtures at subzero temperatures the rate-limidng step is deacylation. It is this step which is most seriously affected by temperature, allowing the acyl-enzyme to accumulate relatively rapidly at — 55°C but to break down very slowly. Amide substrates display different kinetic behavior the slow step is acylation itself. It was predicted that use of a />-nitrophenyl amid substrate would give the structure of the pre-acyl-enzyme Michaelis complex or even the putadve tetrahedral intermediate (Alber et ai, 1976), but this experiment has not yet been carried out. Instead, over the following 7 years, attention shifted to the smaller enzyme bovine pancreatic ribonuclease A. [Pg.332]

Figure 6.7 Catalytic triad involved in elastase action.

Alpha-l-antiprotease (ai-AP) limits tissue damage arising from the actions of the leucocyte protease, elastase (Carrell and Travis, 1985), and there is much evidence available for the oxidative inactivation of this protein by oxygen-derived free-radical species and hypochlorous acid/hypochlorite anion (HOCl/OCP). The mechanism of this inactivation appears to involve the oxidation of a critical methionine residue (Met-358) to its corresponding sulphoxide and methionine sulphoxide has been detected in ai-AP samples isolated from the lungs of cigarette smokers (Carp et al., 1982) and rheumatoid synovial fluids (Wong and Travis, 1980). [Pg.4]

Vergely, I. Laugaa, P. Reboud-Ravaux, M. Interaction of human leukocyte elastase with a /V-aryl azetidinone suicide substrate conformational analyses based on the mechanism of action of serine proteinases. j. Mol. Graphics 1996, 14, 158-167. [Pg.384]

El Ouriaghli F, Fujiwara H, Melenhorst JJ, Sconocchia G, Hensel N, Barrett AJ. Neutrophil elastase enzymatically antagonizes the in vitro action of G-CSF implications for the regulation of granulopoiesis. Blood 2003 101(5) 1752-1758. [Pg.134]

In resting neutrophils, about 50% of the total cellular FcyRIII pool is expressed on the cell surface. There is considerable variation in this value because many methods used to isolate neutrophils can also inadvertently mobilise these subcellular receptors. The remainder of the total cellular FcyRIII that is not expressed on the plasma membrane is present in the subcellular pool. However, if the FcyRIII normally present on the plasma membrane is cleaved (e.g. via the action of elastase or pronase) and the cells subsequently activated, then FcyRIII reappears on the cell surface via the mobilisation of these pools. Thus, the expression can be restored to up to 70% of the resting level within 15 min via such a translocation. During activation (and presumably priming), FcyRIII (together with other plasma membrane markers) is also translocated to the plasma membrane however, because the receptor is also shed from the cell, the total number of receptors on the cell surface remains largely unchanged. There is also some evidence that continued expression of FcyRIII on the cell surface requires de novo biosynthesis of this receptor (see Fig. 7.8). [Pg.122]

Role of ai-AT in the lungs In the normal lung, the alveoli are chronically exposed to low levels of neutrophil elastase released from activated and degenerating neutrophils. This proteolytic activity can destroy the elastin in alveolar walls if unopposed by the inhibitory action of a-rAT, the most important inhibitor of neu trophil elastase (see Figure 4.14). Because lung tissue cannot regenerate, emphysema results from the destruction of the con nective tissue of alveolar walls. [Pg.50]

The reverse action of a trypsin-free elastase isolated from porcine pancreas was studied in frozen aqueous systems and was found to catalyze peptide bond formation more effectively than in solution at room temperature (Haensler, 1998). The acceptance of free amino acids as nucleophilic amino components indicates a changed specificity of the endoprotease in frozen reaction mixtures. In elastase-catalyzed formation of Ser-, lie-, and Val-X-bonds in frozen aqueous reaction mix-... [Pg.359]

A. M. Blow. Action Of human lysosomal elastase on the oxidized B chain of insulin. Buchan. / 7 7 13(1977). [Pg.327]

Serine proteases, released from immune cell granules, process cytokines and growth factors that control multiple cellular process [56], Proteinase 3, cathepsin G, and elastase all cleave membrane-bound TNF-o, IL-1, and IL-18, and activate epidermal growth factor receptor (EGFR) and toll-like receptor-4 (TLR-4). These actions inhibit growth and lead to apoptosis with transcriptional nuclear factor kB (NF-kB) inactivation. Bik suppresses release of TNF-o, IL-1, and IL-18 and prevents EGFR and TLR-4 activation. Activation of NF-kB is a mediator of cell proliferation, whereas inhibition of NF-/. B leads to apoptosis [82]. Overall, Bik inhibition of immune cell serine proteases increases cell proliferation and stability. [Pg.233]

This indicated clearly that hydroxylapatite crystallites are associated intimately with elastin fibers. In the hope of tracing this assocnation to the molecular level the fibers were dissolved by the action of elastase. Brief treatment of elastic fibers with this enzyme yields a soluble, non-dialyzable protein (Partridge et al., 1955) and it was found that after elastase treatment followed by centrifugation to remove particulate matter the soluble protein produced still contained calcium and still displayed... [Pg.246]

Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...