Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Defensins are antibiotic peptides expressed in human and animal myeloid and epithelial cells. Due to the limited availability of natural peptides, the properties of human epithelial defensins have not been studied. We assayed the microbicidal activity of recombinant human intestinal defensin 5 (rHD-5) in the presence of salt (O to 150 mM NaCl) with varied pH (pH 5.5 to pH 8.5) and trypsin (25 and 250 microg/ml). rHD-5 exhibits microbicidal activity against Listeria monocytogenes, Escherichia coli, and Candida albicans. In contrast to cryptdins, the mouse intestinal defensins, rHD-5 is active against both mouse-virulent wild-type Salmonella typhimurium and its isogenic, mouse-avirulent phoP mutant. In the presence of salt, rHD-5 activity was reduced, and at 100 mM NaCl, activity against S. typhimurium was abolished. However, at all salt concentrations tested, rHD-5 remained bactericidal to L. monocytogenes. Activity against L. monocytogenes was not pH dependent but was diminished at pH 5.5 against wild-type S. typhimurium. This acid-induced resistance may have been mediated by the virulence gene regulator phoP, since the phoP mutant was equally sensitive at pH 5.5 and pH 7.4. In the presence of trypsin, rHD-5 was partially cleaved, but even then, rHD-5 at 100 microg/ml decreased the number of CFU of wild-type S. typhimurium by more than 99%. The persistence of microbicidal activity of rHD-5 under these conditions supports the notion that naturally occurring human intestinal defensin is an effective arm of mucosal host defense.
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PMID:Broad-spectrum antimicrobial activity of human intestinal defensin 5. 916 80

The antimicrobial peptide human alpha-defensin 5 (HD5) is expressed in Paneth cells, secretory epithelial cells in the small intestine. Unlike other characterized defensins, HD5 is stored in secretory vesicles as a propeptide. The storage quantities of HD5 are approximately 90 450 microg per cm2 of mucosal surface area, which is sufficient to generate microbicidal concentrations in the intestinal lumen. HD5 peptides isolated from the intestinal lumen are proteolytically processed forms--HD5(56-94) and HD5(63-94)--that are cleaved at the Arg55-Ala56 and Arg62-Thr63 sites, respectively. We show here that a specific pattern of trypsin isozymes is expressed in Paneth cells, that trypsin colocalizes with HD5 and that this protease can efficiently cleave HD5 propeptide to forms identical to those isolated in vivo. By acting as a prodefensin convertase in human Paneth cells, trypsin is involved in the regulation of innate immunity in the small intestine.
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PMID:Paneth cell trypsin is the processing enzyme for human defensin-5. 1203 62

alpha-Defensin is an antimicrobial peptide which plays an important role in innate immunity. Human defensin (HD)-5 is stored in the Paneth cells of the small intestine as a pro-form and is cleaved by trypsin, which is co-secreted from the Paneth cell granules. The mature HD-5 is protected from further digestion by the proteolysis enzyme. We generated both recombinant HD-5 and proHD-5, and the reduced form of each peptide in order to determine their physiological roles of the disulfide bonds. The reduced proHD-5 attenuated the bactericidal activity and the stability against the trypsin digestion. Human defensin was protected from the enzymatic degradation by disulfide bridges. We further purified the HD-5 with a disulfide variation in the small intestine of Crohn's disease patients. The HD-5 was sensitive to the trypsin treatment. These observations evidently predict that a defensin deficiency may be caused by a disulfide disorder in the disease.
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PMID:Denatured human alpha-defensin attenuates the bactericidal activity and the stability against enzymatic digestion. 1748 39

Human defensin (HD)-5 is an antimicrobial peptide expressed in small intestinal Paneth cells, and alterations in HD-5 expression may be important in Crohn's disease (CD) pathogenesis. Levels of HD-5 in Paneth cells and ileostomy fluid from control and CD patients were studied by quantitative immunodot analysis, immunohistochemistry, acid urea-polyacrylamide gel electrophoresis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis Western blotting, reverse phase-high performance liquid chromatography, N-terminal amino acid sequencing, and ES-QToF mass spectrometry. In both control and CD patients, HD-5 in Paneth cell extracts was present almost exclusively in the precursor form. HD-5 levels in ileostomy fluid were lower in CD patients (n = 51) than in controls (n = 20): median (range), 7.9 (5.5 to 35.0) microg/ml versus 10.5 (6.0 to 30.4) microg/ml; P = 0.05; this difference was most marked in CD patients with homozygous/compound heterozygous mutations in NOD2 (P = 0.03). In control ileostomy fluid, HD-5 was present in the mature form only. In contrast, CD patient ileostomy fluid contained both precursor and mature forms of HD-5, with the majority present in a complex with trypsin, chymotrypsinogen/chymotrypsin, and alpha1-anti-trypsin. Pro-HD-5 was not associated with trypsin or chymotrypsinogen in Paneth cell extracts. In conclusion, pro-HD-5 in the intestinal lumen is processed by trypsin in a complex in which chymotrypsinogen is also cleaved for activation. The persistence of this complex in CD may be attributable to increased luminal levels of proteinase inhibitors such as alpha1-anti-trypsin.
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PMID:Impaired luminal processing of human defensin-5 in Crohn's disease: persistence in a complex with chymotrypsinogen and trypsin. 1825 45

Mammalian alpha-defensins, expressed primarily in leukocytes and epithelia, play important roles in innate and adaptive immune responses to microbial infection. Six invariant cysteine residues forming three indispensable disulfide bonds and one Gly residue required structurally for an atypical beta-bulge are totally conserved in the otherwise diverse sequences of all known mammalian alpha-defensins. In addition, a pair of oppositely charged residues (Arg/Glu), forming a salt bridge across a protruding loop in the molecule, is highly conserved. To investigate the structural and functional roles of the conserved Arg(6)-Glu(14) salt bridge in human alpha-defensin 5 (HD5), we chemically prepared HD5 and its precursor proHD5 as well as their corresponding salt bridge-destabilizing analogs E14Q-HD5 and E57Q-proHD5. The Glu-to-Gln mutation, whereas significantly reducing the oxidative folding efficiency of HD5, had no effect on the folding of proHD5. Bovine trypsin productively and correctly processed proHD5 in vitro but spontaneously degraded E57Q-proHD5. Significantly, HD5 was resistant to trypsin treatment, whereas E14Q-HD5 was highly susceptible. Further, degradation of E14Q-HD5 by trypsin was initiated by the cleavage of the Arg(13)-Gln(14) peptide bond in the loop region, a catastrophic proteolytic event resulting directly in quick digestion of the whole defensin molecule. The E14Q mutation did not alter the bactericidal activity of HD5 against Staphylococcus aureus but substantially enhanced the killing of Escherichia coli. By contrast, proHD5 and E57Q-proHD5 were largely inactive against both strains at the concentrations tested. Our results confirm that the primary function of the conserved salt bridge in HD5 is to ensure correct processing of proHD5 and subsequent stabilization of mature alpha-defensin in vivo.
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PMID:The conserved salt bridge in human alpha-defensin 5 is required for its precursor processing and proteolytic stability. 1849 68

Human defensin 5 (HD5) is a 32-residue cysteine-rich host-defense peptide that exhibits three disulfide bonds in the oxidized form (HD5ox). It is abundant in small intestinal Paneth cells, which release HD5 into the intestinal lumen and house a labile Zn(II) store of unknown function. Here, we consider the redox properties of HD5 and report that the reduced form, HD5red, is a metal-ion chelator. HD5 has a midpoint potential of -257 mV at pH 7.0. HD5red utilizes its cysteine residues to coordinate one equivalent of Zn(II) with an apparent Kd1 value in the midpicomolar range. Zn(II) or Cd(II) binding perturbs the oxidative folding pathway of HD5red to HD5ox. Whereas HD5red is highly susceptible to proteolytic degradation, the Zn(II)-bound form displays resistance to hydrolytic breakdown by trypsin and other proteases. The ability of a reduced defensin peptide to coordinate Zn(II) provides a putative mechanism for how these peptides persist in vivo.
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PMID:Reduction of human defensin 5 affords a high-affinity zinc-chelating peptide. 2384 78