Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

The tyrosinase activity in two sucrose gradient isolated melanosome fractions from a melanotic hamster melanoma was found to increase after alpha-chymotrypsin treatment. The enhancement in tyrosinase activity had its maximum at a concentration of 1 mg/ml alpha-chymotrypsin after 120 min incubation at 37 degrees C. No direct activating effect of alpha-chymotrypsin was found either on the soluble tyrosinase fraction from freshly prepared untreaed whole-tumor homogenate or on purified mushroom tyrosinase. The activating effect of alpha-chymotrypsin upon the melanosome tyrosinase is believed to be due to the endopeptidic hydrolysis of the--CO--NH--bound existing between tyrosinase and tyrosine and phenylalanine residues in the melanin molecule. Although alternative interpretations are not excluded, the observed enhancement in tyrosinase activity after alpha-chymotrypsin treatment of melanosomes might indicate the existence of an "enzyme liberating" mechanism in the melanosomes.
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PMID:Chymotrypsin activation of melanosome tyrosinase in hamster melanotic melanoma. 11 73

The possible mitogenic activity of fibronectin (FN) in human primary and metastatic melanoma lines and clones and the involvement of integrins in mediating this effect were evaluated. Quescent human melanoma cells cultured in serum-free medium proliferated in a dose- and time-dependent fashion to immobilized FN as indicated by [3H]thymidine incorporation, increment of cell number, and cell cycle analysis. This response to FN was observed with tumor clones isolated from a subcutaneous metastasis and with primary or metastatic melanomas from different patients, but only when tumor cells expressed the alpha 5 subunit of the FN receptor (i.e., VLA-5). Proliferation to FN by a primary tumor (Me4405) expressing all FN receptors and by a tumor clone (2/60) lacking only the alpha 4 subunit was inhibited by monoclonal antibodies to the alpha 5 and beta 1 but not by monoclonal antibodies to other subunits of FN receptors. Mapping of FN regions responsible for the proliferative signal was performed by stimulating melanoma cells with different FN proteolytic fragments and indicated that a significant mitogenic signal was provided by the M(r) 120,000 alpha-chymotrypsin fragment containing the Arg-Gly-Asp sequence. The proliferation of melanoma cells to FN and to FN fragments was also significantly inhibited by peptides containing the Arg-Gly-Asp sequence. These data indicate that FN can stimulate the proliferation of quiescent melanoma cells and that integrins as alpha 5 beta 1 are involved in the response of tumor cells to this extracellular matrix protein.
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PMID:Role of the alpha 5 beta 1 integrin receptor in the proliferative response of quiescent human melanoma cells to fibronectin. 138 57

Lymphokine activated killer (LAK) cells mediate the lysis of a variety of histologically distinct tumor targets. We investigated the nature and diversity of the structures involved in the recognition phenomenon by evaluating the effects of treating effector and target cells with trypsin and chymotrypsin, enzymes that disrupt surface protein molecules. Chymotrypsin and trypsin treatment of B16 target cells, a murine melanoma cell line, significantly abolished killing by LAK cells. Alternatively, neither of these treatments in P815 cells, a murine mastocytoma cell line, affected killing by LAK cells. Moreover, we found a differential effect of both these enzymes on YAC-1 cells, a murine leukemia cell line, with trypsin having a less inhibitory effect on cytolysis than chymotrypsin. The nature of the LAK cell receptor that presumably plays a role in binding target antigen was also investigated. Treatment of LAK cells with chymotrypsin significantly reduced lysis of the B16 and YAC-1 target cell types. However, trypsin treatment of the effectors only inhibited killing of the B16 tumor cell line. Cytotoxicity exerted against YAC-1 remained unaltered upon trypsinization of LAK cells. These cumulative results indicate heterogeneity of both the receptors on the LAK cells and the surface antigen molecules recognized on these targets. The use of YAC-1 as a target provided us with a tool to compare the LAK with the natural killer (NK) systems. The overall effect of proteolytic enzyme treatment in reducing cell lysis was more pronounced in the NK than in the LAK system.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Heterogeneity of cell surface structures involved in cytotoxicity mediated by lymphokine activated killer cells. 218 Oct 73

We investigated Plasmodium falciparum parasitized erythrocyte binding to proteolytic fragments of thrombospondin and the effects of anti-thrombospondin monoclonal antibodies on this binding. Purified human platelet thrombospondin was cleaved by trypsin, chymotrypsin or thrombin. Fragments were separated by heparin-agarose affinity chromatography, removing the amino-terminal heparin-binding region. Trypsin at 5.0 micrograms ml-1 of thrombospondin cleaved thrombospondin to reduced 140 and 120 kDa fragments plus a reduced 25-kDa heparin-binding fragment. Infected erythrocytes bound to intact thrombospondin (3420 +/- 460 infected erythrocytes mm-2) and the carboxy-terminal fragment, yielding 120-140-kDa fragments on sulfhydryl reduction, but not to the 25-kDa fragment (144 +/- 104 infected erythrocytes mm-2 (mean +/- s.d., N = 4). Similar results were obtained with chymotrypsin and thrombin cleavage. When the anti-thrombospondin monoclonal antibody MA-I was added to immobilized thrombospondin prior to infected erythrocytes, adherence was inhibited by 99%. At the same concentration, MA-I inhibited adherence to C32 melanoma cells by only 35%. MA-I binds to a calcium-dependent structure at the C-terminal globular region of thrombospondin. Monoclonal antibody MA-II inhibited adherence to thrombospondin by 46%, while MA-III had no effect. These antibodies bind to the N-terminal globular region which includes the heparin-binding site and the segment connecting the two globular regions, respectively. The site(s) for infected erythrocyte binding on thrombospondin reside in the large, 140- or 120-kDa, proteolytic cleavage fragments, and not in the N-terminal heparin-binding region.
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PMID:Falciparum malaria parasitized erythrocytes bind to a carboxy-terminal thrombospondin fragment and not the amino-terminal heparin-binding region. 219 22

A new, sensitive assay based on the enzyme-linked immunosorbent assay has been developed for measuring elastolytic activity produced by invasive and/or metastatic tumor cells in culture. Elastin peptides, obtained by treating the insoluble protein with either oxalic acid, KOH, or chymotrypsin, are adsorbed onto the surface of cell culture microtiter plastic wells, and incubated with dilution of standard proteinases or viable normal or tumor cells. The total amount of immobilized elastin peptides is revealed by the mean of specific antibodies, and detected by a microplate reader, while dose- and time-dependent reduction of bound antibodies after incubation with proteases or cells is taken as a measure of elastin degradation. Adsorbed elastin has been found to be available as a substrate for purified enzymes, as well as for living melanoma cells (A2058 and B16-BL6), c-Ha-ras transformed rat embryo fibroblasts, and human pulmonary macrophages, as demonstrated by the release into the culture medium of lower molecular weight digestion products. No degradation was achieved by BALB/3T3 and rat embryo control fibroblasts, and no inhibition was produced by the presence of fetal calf serum which, on the contrary, potentiated the degradation by active cells. This new method, revealing degradation of only a few nanograms of soluble elastin peptides, can be used for studying the importance in tissue invasion and metastasis of elastolytic proteinases produced by cells in culture.
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PMID:Degradation of immobilized soluble elastin by tumor cells in culture: quantitation by ELISA. 239 16

Activity of peritoneal plasminogen activator and its regulation by dextran and other macromolecules that clinically suppress postoperative adhesions was studied. Plasminogen activator activity was assayed by a two-stage globinolytic assay that monitors formation of plasmin, as well as by cleavage of a chromogenic peptide substrate (S-2444) in the presence of aprotinin (Trasylol). Plasminogen activator activity was located on the outer surface of human peritoneum. Incubation of peritoneal tissue with buffer in vitro (conditioning) prompted release of plasminogen activator into the conditioning medium. The released plasminogen activator formed a single band on sodium dodecyl sulfate-gel electrophoresis at an apparent molecular weight of 174,000 and was markedly suppressed by antiserum raised against human melanoma tissue-type plasminogen activator. Nonspecific proteolytic activity did not accumulate in the medium during conditioning. The presence of dextran 80 during conditioning of peritoneum reversibly suppressed tissue-bound plasminogen activator activity and reduced plasminogen activator activity in the spent medium. A similar inhibition of peritoneal plasminogen activator was induced by dextran 500, methyl cellulose, and polyvinylpyrrolidone. Dextran, when added to the medium after conditioning, had no direct inhibitory effect on plasminogen activator activity. Dextran did not induce peritoneal production of inhibitor(s) of trypsin, chymotrypsin, or urokinase. On the basis of these findings, two possible mechanisms for the effect of viscous polymers in the reduction of adhesion formation are proposed. These mechanisms consider the importance of peritoneal tissue-type plasminogen activator for removal of fibrin clots and suggest that polymer coating either prevents the shedding of plasminogen activator into the abdominal cavity or reduces the access of fibrin clots to the serosal surfaces.
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PMID:Effect of viscous macromolecules on peritoneal plasminogen activator activity: a potential mechanism for their ability to reduce postoperative adhesion formation. 245 68

Two analogues of alpha-MSH (Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2), Ac-[Nle4, Asp5, D-Phe7, Lys10]alpha-MSH4-10NH2 and Ac-[Nle4, Asp5, D-Phe7, Lys10] alpha-MSH4-10-NH2, were synthesized, and the melanotropic activities of the peptides were compared in several bioassays. Potencies were determined in the in vitro frog and lizard skin bioassays and in the S91 melanoma cell tyrosinase assay. Both analogues were equipotent or more potent than alpha-MSH in all bioassays, and the activities of the analogues were prolonged compared to alpha-MSH. The two analogues were very resistant to inactivation by purified proteolytic enzymes (alpha-chymotrypsin, trypsin, and pepsin). The two peptides could be topically applied and transdermally delivered across the skin of mice in vivo, resulting in a shift from pheomelanogenesis to eumelanogenesis within follicular melanocytes. The cyclic analogue exhibited greater potency, prolonged activity, and stability against enzyme inactivation than did the linear peptide. The significance of the findings for the further design of melanotropin analogues is discussed, as in the possible relevance of these melanotropin analogues for use in biomedical studies.
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PMID:Linear and cyclic alpha-melanotropin [4-10]-fragment analogues that exhibit superpotency and residual activity. 255 3

The fluorescein-labeled melanotropin [N alpha-chlorotriazinylaminofluorescein-Ser1,Nle4,D-Phe 7]-alpha-MSH, was prepared by solid-phase techniques of peptide synthesis. The biological actions of this analogue were determined in several melanocyte bioassays and were compared with the parent peptide [Nle4,D-Phe7]-alpha-MSH and the native hormone alpha-MSH. The fluorescein compound was a superpotent agonist with approximately 10 times more activity than alpha-MSH in both the frog and the lizard skin bioassays. Murine S91 melanoma cells assayed in vitro (tyrosinase bioassay) were as responsive to the fluorescein analogue as to alpha-MSH. The analogue exhibited ultraprolonged biological activity and the biological activities were unaffected by treatment of the analogue with alpha-chymotrypsin. The fluorescein-labeled melanotropin should prove useful for melanotropin receptor characterization.
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PMID:Synthesis and biological evaluation of the superagonist [N alpha-chlorotriazinylaminofluorescein-Ser1,Nle4,D-Phe7]-al pha-MSH. 298 82

The isoenzyme profiles of tyrosinase isolated from melanosomal and cytoplasmic fractions of hamster melanoma were investigated. The liberation of the enzyme from the melanosomal membranes was achieved by their treatment with Triton X-100 or alpha-chymotrypsin. The isoenzyme spectrum of tyrosinase liberated by use of Triton X-100 from melanosomes differing in the degree of melanization is identical to that of the cytoplasmic enzyme and gives three peaks on a densitogram. The liberation of melanosomal tyrosinase by alpha-chymotrypsin results in the appearance of an additional isoenzyme due to proteolytic degradation. The role of tyrosinase isoenzymes in the synthesis of melanin is discussed.
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PMID:[Isoenzymes of melanosomal tyrosinase isolated from transplanted hamster melanomas]. 643 Mar 55

Biocytin derivatives of a superpotent analogue of alpha-melanotropin, [Nle4,D-Phe7]-alpha-MSH, were prepared. [N alpha-Bct-Ser1, Nle4,D-Phe7]-alpha-MSH and [12-Bct-N alpha-dodecanoyl-Ser1,Nle4,D-Phe 7]- alpha-MSH were synthesized by solid-phase techniques, and the coupling of biotin and 12-aminododecanoic acid was achieved through their succinimido esters. These melanotropins possessed almost identical actions to [Nle4,D-Phe 7]- alpha-MSH as determined by several melanocyte bioassays. Both biocytin derivatives were highly potent agonists and exhibited prolonged biological activity as determined in the frog and lizard skin bioassays. Both biotinylated peptides were at least equipotent to alpha-MSH in stimulating Cloudman S91 mouse melanoma tyrosinase activity. The analogues were resistant to inactivation by alpha-chymotrypsin.
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PMID:Synthesis and biological actions of highly potent and prolonged acting biotin-labeled melanotropins. 643 88


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