Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.4.21.1 (chymotrypsin)
 10,938 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A chymotrypsin-derived and 125I-labelled 125-kDa fragment of human plasma fibronectin which contained the cell binding site, was only weakly bound by peritoneal macrophages of guinea pigs and binding was not saturable. In presence of wheat germ lectin binding increased proportionally to the logarithm of the lectin concentration. Association of 125I-fragment with cells was partially prevented by non-labelled fragment indicating a saturable receptor-ligand interaction. An apparent affinity constant of about 2--4 x 10(-5) M was evaluated. A considerable fraction of the cell-bound 125I-fragment resisted removal by proteases suggesting that it was internalized. In order to investigate an influence of wheat germ lectin on the binding of 125I-fibronectin by the cells the macrophages were preincubated with the lectin followed by washing and evaluation of 125I-fibronectin binding. A simultaneous incubation of the cells with 125I-fibronectin and lectin was impractical due to partial interaction of the two proteins giving rise to some unspecific precipitates. Preincubation with wheat germ lectin considerably improved the capacity of the macrophages for binding of 125I-fibronectin. Again the binding of 125I-labelled protein could be restricted by unlabelled one. N-acetyl-glucosamine inhibited the binding of 125I-fibronectin by wheat germ lectin-treated cells if applied in the preincubation phase and more effectively, if applied in the final 125I-fibronectin binding assay. N-Acetylneuraminic acid also inhibited this step. In addition to wheat germ lectin concanavalin A was capable of generating fibronectin receptors on the cell surface. Soy bean lectin, however, was ineffective.
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PMID:Generation of fibronectin receptors on macrophages by wheat germ lectin. 631 9

Induction of the neutral proteinase, collagenase, is a marker for a specific switch in gene expression observed in rabbit synovial fibroblasts. A variety of agents, including 12-O-tetradecanoylphorbol-13-acetate, cytochalasins B and D, trypsin, chymotrypsin, poly(2-hydroxyethylmethacrylate), and trifluoperazine induced this change in gene expression. Induction of collagenase by these agents was always correlated with a marked alteration in cell morphology, although the cells remained adherent to the culture dishes. The amount of collagenase induced was positively correlated with the degree of shape change produced by a given concentration and, to some extent, with the duration of treatment. Altered cell morphology was required only during the first few hours of treatment with inducing agents; after this time collagenase synthesis continued for up to 6 d even when agents were removed and normal flattened cell morphology was regained. All agents that altered cell morphology also produced a characteristic switch in protein secretion phenotype, characterized by the induction of procollagenase (Mr 53,000 and 57,000) and a neutral metalloproteinase (Mr 51,000), which accounted for approximately 25% and 15% of the protein secreted, respectively. Secretion of another neutral proteinase, plasminogen activator, did not correlate with increased collagenase secretion. In contrast, synthesis and secretion of a number of other polypeptides, including the extracellular matrix proteins, collagen and fibronectin, were concomitantly decreased. That changes in cell shape correlated with a program of gene expression manifested by both degradation and synthesis of extracellular macromolecules may have broad implications in development, repair, and pathologic conditions.
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PMID:Changes in cell shape correlate with collagenase gene expression in rabbit synovial fibroblasts. 632 18

Previous studies of the binding properties of fibronectin (Fn) have utilized methods whereby one or the other macromolecule was immobilized on a solid phase. In order to examine the interaction between human plasma Fn and gelatin in solution, the latter was labeled with fluorescein isothiocyanate (FITC) whose fluorescence polarization (P) served as a sensitive indicator of the formation of soluble complexes. Changes in P were detectable at Fn concentrations below 10(-9) M and continued up to concentrations above 10(-6) M at pH 7.3 and 25 degrees C. Fractionation of FITC-gelatin by exclusion chromatography and titration of selected fractions revealed a trend towards higher affinity with increasing size. A high-molecular-weight fraction comprised of beta and gamma components and a low-molecular-weight fraction comprised primarily of alpha chains exhibited sigmoidal increases in P (apparent positive cooperativity) with 50% saturation near 10(-9) and 10(-8) M Fn, respectively. By contrast, a 42-kDa chymotrypsin-generated Fn fragment which retains the ability to adhere to gelatin-Sepharose exhibited normal (noncooperative) binding to both gelatin fractions with Kd = 7 X 10(-7) M. In all cases, the increase in P could be reversed by addition of excess unlabeled gelatin or urea. The interaction of FN with FITC-gelatin provides the basis for a fast and sensitive determination of Fn levels in plasma and other fluids. Interference caused by other proteins such as albumin, which has an affinity for the fluorescein moiety, could be minimized by addition of 1.0 M NaCl which had no effect on the interaction between Fn and gelatin.
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PMID:Fluid-phase interaction between human plasma fibronectin and gelatin determined by fluorescence polarization assay. 636 82

The binding of Candida albicans yeast cells to human fibronectin (Fn), a major glycoprotein of mammalian cells, was studied using an in vitro assay. Adherence was quantitated in microtiter dishes coated with Fn to which radiolabeled yeast cells were added. Under optimum conditions of the assay, i.e., 1 mM CaCl2 and 70 micrograms Fn protein, approximately 40% of the radiolabeled yeast cells adhered to the Fn. Adherence to Fn was greater at 30 degrees C than at 4 degrees C and was greater with viable yeast cells than with heat-killed cells. Candida albicans (two strains) and C. tropicalis adhered to Fn to a greater extent than C. pseudotropicalis, C. krusei, or Saccharomyces cerevisiae. Pretreatment of C. albicans with chymotrypsin, pronase, or papain, but not pepsin, decreased adherence to Fn. Blocking experiments using mannan, sugars, or amino sugars were carried out by preabsorbing the Fn with each of the above-mentioned compounds. Candida mannan blocked adherence of C. albicans to Fn. The mannan effect was dose dependent. However, adherence of C. albicans to Fn was not significantly reduced by mannose, glucose, or several other sugars. The role of FN as a receptor for the binding of C. albicans yeast cells to buccal and vaginal epithelial cells was investigated also using an in vitro assay. We determined, using indirect fluorescent antibody techniques, that both buccal and vaginal epithelial cells possessed Fn. In addition, yeast cells, when pretreated with Fn, showed reduced adherence with buccal and vaginal cells when compared with nontreated cells. These studies may indicate a role for Fn in the adherence of C. albicans to buccal and vaginal epithelial cells.
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PMID:In vitro binding of Candida albicans yeast cells to human fibronectin. 637 Mar 99

Pretreatment of hemoglobin with 50-5000 nmol hydrogen peroxide (H2O2) increased its susceptibility to proteolysis by a number of purified enzymes, including trypsin, chymotrypsin, elastase, and plasmin, and by the neutral protease of rat peritoneal leukocytes. Pretreatment of the protein substrate with catalase-inactivated H2O2 had no effect. Separation of the proteolytic fragments by G-75 Sephadex gel filtration indicated no apparent differences in the size distribution of the fragments produced by treatment with the H2O2/proteolytic enzyme combination as compared with enzyme treatment alone. A partially purified preparation of rat glomerular basement membrane was also treated with proteolytic enzyme alone or in combination with H2O2. As with the hemoglobin, pretreatment of the glomerular basement membrane with H2O2 increased its susceptibility to subsequent proteolytic attack. In addition, treatment of a basement membrane glycoprotein, fibronectin, with H2O2 also increased its sensitivity to subsequent proteolysis. These results suggest that in addition to their other proinflammatory activities, oxygen-derived metabolites may contribute to tissue destruction by altering the susceptibility of proteins to hydrolytic enzymes.
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PMID:Protein degradation following treatment with hydrogen peroxide. 637 92

Previous studies demonstrating that a continuous line of human monocyte-like cells (U937) and human monocytes contain elastase probably identical to human neutrophil elastase suggested the possibility that mononuclear phagocytes share other proteinases with neutrophils. The present work establishes that U937 cells contain cathepsin G, an enzyme heretofore found only in neutrophils. U937 cells contain approximately 10 micrograms of cathepsin G-like activity per 10(7) cells, about 25% of the cathepsin G activity in human neutrophils. Normal monocytes have minimal cathepsin G-like activity (approximately 0.1 microgram per 10(7) cells). The cathepsin G-like activity of U937 cells appears to be due to an enzyme that is the same as cathepsin G by several criteria: 1) it is a serine proteinase with activity like cathepsin G against a synthetic chymotrypsin substrate, succinyl-ala-ala-pro-phe-p-nitroanilide; 2) the proteolytic fragments it releases from fibronectin match those released by cathepsin G; 3) like cathepsin G, it can be purified by sequential Trasylol-Sepharose affinity chromatography and carboxymethyl-Sephadex ion exchange chromatography; 4) its amino acid composition and migration on SDS-polyacrylamide gel electrophoresis are indistinguishable from cathepsin G; and 5) it binds with antiserum raised to cathepsin G. The presence of cathepsin G in U937 cells, in much higher concentration than in normal monocytes, indicates either that the content of cathepsin G in monocytes decreases markedly during monocyte differentiation or that U937 cells differ from normal immature monocytes with respect to synthesis of this neutral proteinase.
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PMID:Cathepsin G in human mononuclear phagocytes: comparisons between monocytes and U937 monocyte-like cells. 656 54

Limited proteolysis of human plasma fibronectin with chymotrypsin, trypsin or thermolysin has been used to localize binding sites responsible for binding [Vuento, Korkolainen & Stenman (1982) Biochem. J. 205, 303-311] of fibronectin to carboxy-group-modified proteins. These bindings sites are different from those mediating binding of fibronectin to gelatin or heparin. They are located close to the C-terminus of the polypeptide chains of fibronectin, and apparently overlap with the C-terminal fibrin binding site.
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PMID:Identification of fibronectin fragments that bind to carboxy-group-modified proteins. 666 Nov 87

Thrombospondin (TS), a protein first described in platelets, was recently shown to be synthesized and secreted by endothelial cells, fibroblasts, and smooth muscle cells. The presence of TS in the extracellular matrix of cultured cells has prompted us to examine the associations of this protein with matrix macromolecules. Interactions of TS with both matrix and serum proteins were tested using an enzyme-linked immunosorbent assay. With this assay we assessed the binding of TS in solution to proteins adsorbed to polystyrene microtiter plates. Among collagens, platelet TS bound to type V but not to types I, III, or IV. This selective interaction was confirmed in experiments using proteins linked to cyanogen bromide-activated Sepharose. TS released from platelets in response to thrombin activation, as well as that secreted by endothelial cells in culture, bound to type V but not to type I collagen-Sepharose. No binding was observed to denatured type V collagen-Sepharose. The binding region for type V collagen was located in a chymotrypsin-produced fragment of TS with chains of Mr = 70,000, after reduction. Interactions of TS with a number of other proteins, including fibronectin, fibrinogen, and laminin, could be demonstrated using the enzyme-linked immunosorbent assay technique but the interpretation of these findings is difficult since comparable binding to protein-Sepharose was not always observed. Our findings suggest that both the extravascular distribution and function of TS in vivo may involve an interaction with type V collagen.
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PMID:Interactions of thrombospondin with extracellular matrix proteins: selective binding to type V collagen. 669 1

Medium conditioned by tissue from the CNS of the snail, Helisoma, is capable of promoting neurite outgrowth in isolated neurons from adult central ganglia. The conditioning factor(s) (CF), contained in conditioned medium (CM), is produced only by central ganglionic rings and buccal ganglia and not by other tissues, including hemolymph. CF requires a minimum of 24 h to be produced or released into the medium. At 12 h growth-promoting activity was not detectable. CF binds tightly to the polylysine substratum and its activity is not mimicked by addition of various sera, NGF or fibronectin. CF activity is abolished by chymotrypsin, trypsin or heating to 100 degrees C, but is stable to DNase and RNase treatment. The percentage of cells exhibiting neurite outgrowth is approximately linear with the amount of neural tissue used to condition the medium up to 2 ganglionic rings/ml. Addition of more ganglia fails to stimulate a greater response. This apparent plateau of CM activity appears to be a function of production and/or release of CF, rather than a saturation effect on plated cells, since dose-response curves for dilutions of CM are approximately linear regardless of the number of ganglia used for conditioning. In addition, anisomycin inhibits 35% of CF appearance under conditions of over 90% protein synthesis inhibition in the ganglia used to produce the CM. Under these conditions anisomycin has no apparent effect on the maintenance of electrical excitability. The inhibitor data suggest that 65% of CF is derived from a pre-existing storage pool and that the remainder is synthesized during the 72 h conditioning period.
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PMID:Nerve growth-promoting factor produced in culture media conditioned by specific CNS tissues of the snail Helisoma. 669 14

The complete amino acid sequence of the collagen-binding domain of bovine plasma fibronectin has been determined. The fragment, generated by digestion of fibronectin with plasmin and chymotrypsin, contains 340 residues (260-599 of fibronectin) with threonine and tryptophan as the amino-terminal and carboxyl-terminal amino acids, respectively. 24 half-cystines and no cysteines are present in the sequence. Three glucosamine-based oligosaccharide groups are attached to Asn-399, Asn-497 and to Asn-511, respectively. Two of the three types (I and II) [Petersen et al. (1983) Proc. Natl Acad. Sci. USA 80, 137-141] of internal homology occur in the fragment, namely four of the at least twelve stretches of type I sequence homology, 'fingers', and two stretches of type II homology. The type I homology is present in two other plasmic fragments from fibronectin, while the type II homology has been found in the collagen-binding domain only.
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PMID:Complete primary structure of the collagen-binding domain of bovine fibronectin. 671 32


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