Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.37 (neutrophil elastase)
 4,078 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Secretory leukoprotease inhibitor (SLPI) is one of the major physiological inhibitors protecting respiratory epithelium from attack by excess human leukocyte elastase (HLE), a serine protease released by neutrophils upon activation in response to inflammatory stimuli. Reaction with N-chlorotaurine, a major long-lived oxidant generated by activated neutrophils, oxidized all four methionine residues, but no other amino acids, in SLPI, resulting in substantial diminution of its elastase inhibitory activity. Oxidation of the P1' residue, Met73, accounted for most of the diminution in activity since a site-directed mutant of SLPI with leucine at the P1' position retained much higher residual activity after reaction with N-chlorotaurine. The diminished activity of oxidized SLPI could be almost completely restored when an iduronate-containing glycosaminoglycan, such as heparin, heparan sulfate, or dermatan sulfate, was added to the reaction medium. Addition of a sulfated glucuronate-containing glycosaminoglycan, chondroitin 4- or 6-sulfate, to the medium resulted in smaller but significant restoration of the lost activity, whereas the effects of hyaluronic acid and keratan sulfate were negligible. Kinetic analysis revealed that glycosaminoglycans greatly accelerated the association of oxidized SLPI and HLE, whereas iduronate-containing glycosaminoglycans also stabilized the enzyme-inhibitor complex formed. Based on these findings, we suggest that oxidized SLPI is a functionally active form of the inhibitor but that expression of its elastase inhibitory activity is regulated by sulfated uronate-containing glycosaminoglycans. Because its methionine residues have already been oxidized, this form of SLPI is resistant to the oxidant species that selectively attacks methionine residues in proteins. These findings indicate that SLPI may play a previously unexpected role in elastase inhibitory function in the lungs when significant inflammation is present.
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PMID:Glycosaminoglycans regulate elastase inhibition by oxidized secretory leukoprotease inhibitor. 912 11

The influence of ionic strength and composition on the binding and inhibition of human leukocyte elastase by glycosaminoglycans with variable degree and position of sulfation was investigated. The kinetic mechanism of inhibition had a hyperbolic, mixed-type character with a competitive component that was promoted by low ionic strength, reduced by phosphate ions, and which also depended on the substrate and glycosaminoglycan structure. Enzyme binding was a cooperative phenomenon that varied with ionic strength and composition. The inhibition patterns correlated with the cationic character of elastase and with the distribution of arginines on its molecular surface, most notably with residues located in the vicinity of the substrate binding region. The order of affinity for elastase binding was chondroitin 4-sulfate < chondroitin 6-sulfate < dermatan sulfate, iduronate-containing derivatives being superior with respect to the glucuronate-containing counterparts. Additional sulfation at both the 4- and 6- positions or at the N- and 4-positions of the N-acetylgalactosamine moiety decidedly improved the inhibitory efficiency. The results highlight a fundamental physiological role of enzyme-glycosaminoglycan interactions. In the azurophil granule of the human polymorphonuclear neutrophil, elastase and other enzymes are bound to a matrix of chondroitin 4-sulfate because this is the only glycosaminoglycan that simultaneously offers good binding for enzyme compartmentalization together with prompt release from the bound state at the onset of phagocytosis.
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PMID:Electrostatic interactions between human leukocyte elastase and sulfated glycosaminoglycans: physiological implications. 946 47