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

Expression of neoantigens during denaturation of IgG by oxygen radicals or proteolysis was assumed to be a possible mechanism for stimulation of rheumatoid factor (RF) formation and/or granulocyte dependent inflammative joint destruction. The so-called human leukocyte elastase (HLE) regularly released by stimulated neutrophils f.e. into the RA synovial fluid is known to split IgG in vitro into papain like fragments and low molecular weight peptides. The n-terminal site of the HLE related Fc is bearing a neoantigenic group which is located near the hinge region but not expressed by the native IgG. The neoantigen itself is represented by the low molecular weight peptides produced by prolonged HLE-IgG proteolysis. Detection of HLE generated Fc in synovial fluids was performed by radioimmunoassay specific for the neoantigen. Patients were divided into the three groups; I RA (n = 23), II inflammative joint effusions except RA (n = 23), III osteoarthritis and trauma (n = 19). The biological effect of the neoantigen on to granulocyte oxidative metabolism was tested by Cytochrome C reduction and chemiluminescence. Neoantigen bearing Fc could be detected in 15 of 23 cases of group I, in group II in 11 of 23 cases and only in 7 of 19 cases in group III. The median concentrations were 0.62 micrograms in group I and zero in II and III. The HLE derived Fc were able to inhibit the oxidative metabolism of activated granulocytes in vitro. The O2- production of stimulated granulocytes was depressed dose dependent by the neoantigen. The neoantigenic group itself does not react with RF as proved by nephelometric titration of HLE derived Fc, neoantigenic peptide and native IgG against a RF standard.
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PMID:Neoantigenic group on Fc fragments in rheumatoid arthritis synovial fluids. 246 51

Human lysosomal elastase cleaves human monoclonal IgG into components that closely resemble the fragments produced by papain digestion. IgG1 produced Fab, Fc and Fab-Fc fragments; cleavage of IgG2 produced F(ab)2, Fab-Fc, Fab and Fc fragments; IgG3 gave rise to almost pure Fab and Fch (Fc covalently joined to the extended hinge region polypeptide of IgG3), and from IgG4, F(ab)2, Fab and Fc fragments were recovered. The relative susceptibilities of the four human IgG subclasses to proteolytic attack by elastase were studied kinetically and showed the following decreasing order of susceptibility: IgG3 > IgG1 > IgG2 > IgG4. The Fab fragment from papain digestion of IgG1 and the corresponding fragment from elastase digestion showed indistinguishable molecular weights and immunochemical identity.
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PMID:Kinetics of the different susceptibilities of the four human immunoglobulin G subclasses to proteolysis by human lysosomal elastase. 690 81

An expression system for alpha 1-antitrypsin in Escherichia coli was developed using a T7 RNA polymerase promoter. Addition of rifampicin to inhibit the E. coli RNA polymerase after induction of the T7 RNA polymerase gene resulted in about 30% of newly synthesized protein being alpha 1-antitrypsin. This expression system was then used to examine the effect of mutations in the hinge region of alpha 1-antitrypsin on its activity. The mutations were based on ones in antithrombin III that had previously been shown to have adverse effects on activity. Mutation of Ala347 to threonine in alpha 1-antitrypsin did not affect the kinetic behavior of the protein with trypsin or human leukocyte elastase. In contrast, mutation of Gly349 to proline converted the majority of the protein into a substrate for both proteinases. The small fraction of this mutant that was active, however, had kinetic parameters that were indistinguishable from wild-type alpha 1-antitrypsin. Cleavage within the reactive-site loop of wild-type alpha 1-antitrypsin causes a conformational change in the molecules (the S-to-R transition) and results in a marked increase in heat stability. This increase in heat stability was also seen upon cleavage within the reactive-site loops of both of the alpha 1-antitrypsin mutants. The results are discussed in terms of a kinetic mechanism for serpin-proteinase interactions, in which after the formation of an initial complex the serpin partitions between the formation of a stable complex and a cleavage reaction.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effects of mutations in the hinge region of serpins. 834 75

Leukocyte elastase inhibitor (LEI) is a cytosolic component of lung macrophages and blood leukocytes that inhibits neutrophil elastase. LEI is a member of the serpin superfamily, these proteins, mostly protease inhibitors, are thought to undergo a conformational change upon complex formation with proteinase that involves partial insertion of the hinge region of the reactive centre loop into a beta-sheet of the inhibitor. In this work three mutations were produced in the hinge region of elastase inhibitor that abolish the inhibition activity of LEI and transform the protein in a substrate of the elastase. This result demonstrates that the inhibitory mechanism of serpin is common to LEI.
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PMID:Mutations on the hinge region of leukocyte elastase inhibitor determine the loss of inhibitory function. 1092 64

Antichymotrypsin (SERPINA3) is a widely expressed member of the serpin superfamily, required for the regulation of leukocyte proteases released during an inflammatory response and with a permissive role in the development of amyloid encephalopathy. Despite its biological significance, there is at present no available structure of this serpin in its native, inhibitory state. We present here the first fully refined structure of a murine antichymotrypsin orthologue to 2.1 A, which we propose as a template for other antichymotrypsin-like serpins. A most unexpected feature of the structure of murine serpina3n is that it reveals the reactive center loop (RCL) to be partially inserted into the A beta-sheet, a structural motif associated with ligand-dependent activation in other serpins. The RCL is, in addition, stabilized by salt bridges, and its plane is oriented at 90 degrees to the RCL of antitrypsin. A biochemical and biophysical analysis of this serpin demonstrates that it is a fast and efficient inhibitor of human leukocyte elastase (ka: 4 +/- 0.9 x 10(6) m(-1) s(-)1) and cathepsin G (ka: 7.9 +/- 0.9 x 10(5) m(-1) s(-)1) giving a spectrum of activity intermediate between that of human antichymotrypsin and human antitrypsin. An evolutionary analysis reveals that residues subject to positive selection and that have contributed to the diversity of sequences in this sub-branch (A3) of the serpin superfamily are essentially restricted to the P4-P6' region of the RCL, the distal hinge, and the loop between strands 4B and 5B.
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PMID:The murine orthologue of human antichymotrypsin: a structural paradigm for clade A3 serpins. 1614 Nov 97

A comparative in vitro survey of physiologically relevant human and microbial proteinases defined a number of enzymes that induced specific hinge domain cleavage in human IgG1. Several of these proteinases have been associated with tumor growth, inflammation, and infection. A majority of the identified proteinases converted IgG to F(ab')(2), and a consistent feature of their action was a transient accumulation of a single-cleaved intermediate (scIgG). The scIgG resulted from the relatively rapid cleavage of the first hinge domain heavy chain, followed by a slower cleavage of the second chain to separate the Fc domain from F(ab')(2). Major sites of enzymatic cleavage were identified or confirmed from the mass of the F(ab')(2) or Fab fragments and/or the amino-terminal amino acid sequence of the Fc for each enzyme including human matrix metalloproteinases (MMPs) 3 and 12, human cathepsin G, human neutrophil elastase (Fab), staphylococcal glutamyl endopeptidase I and streptococcal immunoglobulin-degrading enzyme (IdeS). The cleavage sites in IgG1 by MMP-3, cathepsin G and IdeS were used to guide the synthesis of peptide analogs containing the corresponding carboxy-termini to be used as immunogens in rabbits. Rabbit antibodies were successfully generated that showed selective binding to different human F(ab')(2)s and other hinge-cleavage fragments, but not to intact IgG. In Western blotting studies of synovial fluids from individuals with rheumatoid arthritis, the rabbit antibodies yielded patterns consistent with the presence of endogenous IgG fragments including F(ab')(2) and the single-cleaved IgG intermediate. The detection in synovial fluid of IgG fragments similar to those observed in the in vitro biochemical studies suggests that proteolysis of IgG may contribute to localized immune dysfunction in inflammatory environments.
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PMID:Proteolysis of purified IgGs by human and bacterial enzymes in vitro and the detection of specific proteolytic fragments of endogenous IgG in rheumatoid synovial fluid. 1815 32

Corticosteroid-binding globulin (CBG) is a non-inhibitory serine proteinase inhibitor (serpin) that transports cortisol and progesterone in blood. Crystal structures of rat CBG and a thrombin-cleaved human CBG:anti-trypsin (Pittsburgh) chimera show how structural transitions after proteolytic cleavage of the CBG reactive center loop (RCL) could disrupt steroid binding. This ligand release mechanism is assumed to involve insertion of the cleaved RCL into the beta-sheet A of the serpin structure. We have, therefore, examined how amino acid substitutions in the human CBG RCL influence steroid binding before and after its cleavage by neutrophil elastase. Elastase-cleaved wild-type CBG or variants with substitutions at P15 and/or P16 (E334G/G335N or E334A) lost steroid binding completely, whereas deletion of Glu-334 resulted in no loss of steroid binding after RCL cleavage, presumably because this prevents its insertion into beta-sheet A. Similarly, the steroid binding properties of CBG variants with substitutions at P15 (G335P), P14 (V336R), or P12 (T338P) in the RCL hinge were largely unaffected after elastase cleavage, most likely because the re-orientation and/or insertion of the cleaved RCL was blocked. Substitutions at P10 (G340P, G340S) or P8 (T342P, T342N) resulted in a partial loss of steroid binding after proteolysis which we attribute to incomplete insertion of the cleaved RCL. Remarkably, several substitutions (E334A, V336R, G340S, and T342P) increased the steroid binding affinities of human CBG even before elastase cleavage, consistent with the concept that CBG normally toggles between a high affinity ligand binding state where the RCL is fully exposed and a lower affinity state in which the RCL is partly inserted into beta-sheet A.
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PMID:Residues in the human corticosteroid-binding globulin reactive center loop that influence steroid binding before and after elastase cleavage. 1901 Dec 38