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)

We characterized a platelet specific alloantigen (Yukb). In immunoblotting, anti-Yukb antibody was found to react with both 110 kDa and 96 kDa bands under nonreducing condition. Immunoblotting followed by separation by two-dimensional electrophoresis (isoelectric focusing/SDS-PAGE) showed that the 96 kDa band had a pI of 5.1-5.8, while the 110 kDa band had a pI of 5.2-5.7. The 96 kDa band was identified as glycoprotein (GP) IIIa on the basis of periodic acid Schiff staining, but the 110 kDa band was not characterized. These results implied that it is difficult to determine differences in antigenic epitopes between Yukb and PlA1 antigens by the electrophoresis. Yukb antigen, unlike PlA1 antigen, was partially destroyed by chymotrypsin treatment. Furthermore, endoglycosidase H digestion resulted in loss of the Yukb epitope, while the PlA1 determinant was retained on the three bands with lower molecular weights after endoglycosidase H digestion. The transfer of Yukb antigens recognized by anti-Yukb antibody into the supernatant of platelets treated with endoglycosidase H was also found using mixed passive hemagglutination test. The results indicated that the Yukb epitope might be located to the endoglycosidase H digested N-linked high mannose carbohydrate chains of GP IIIa or hybrid type chains of GP IIIa, which is different from the location of PlA1 epitope.
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PMID:Endoglycosidase H digestion of Yukb (Pena) alloantigen. 144 May 20

Patient A.F. is a 28-year-old polytransfused woman with an inherited bleeding disorder, Glanzmann's thrombasthenia. An abnormal platelet function is linked to severe decreases in the platelet content of the integrins GP IIb and GP IIIa. In 1987 the patient gave birth to a child with severe anemia and thrombocytopenia. Serological tests revealed the presence of anti-platelet antibody together with an anti-Rhesus D. Western blotting identified a major antibody that reacted with a protein of 90-95 kDa present in platelets and endothelial cells. This was identified as the beta 3 integrin subunit (GP IIIa). Antibody-binding required intact disulfides, while controlled digestion with proteases showed the determinant(s) to be retained within chymotrypsin- (50, 63 kDa) and Staphylococcus aureus V8 protease-derived (25-38 kDa) fragments of GP IIIa. Direct binding assays performed in the presence of monoclonal antibodies specific for different epitopes on GP IIb-IIIa complexes confirmed that the epitope was exposed on intact platelets and revealed a specific inhibition of A.F. IgG binding by the monoclonal antibody, AP-3. Other tests confirmed that the antibody reacted independently of the PlA or Pen polymorphisms carried by GP IIIa. IgG purified from A.F. plasma by adsorption and elution from paraformaldehyde-fixed normal platelets or electrophoretically separated GP IIIa was an inhibitor of ADP-induced platelet aggregation. Unexpectedly, Western blotting showed trace amounts of abnormally migrating GP IIIa in A.F. platelets, which retained an ability to react with her antibody. This suggests that the patient has formed an autoantibody reactive with an active site of the beta 3 integrin subunit and linked to the development of neonatal thrombocytopenia.
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PMID:Characterization of an antibody to the integrin beta 3 subunit (GP IIIa) from a patient with neonatal thrombocytopenia and an inherited deficiency of GP IIb-IIIa complexes in platelets (Glanzmann's thrombasthenia). 163 70

Two monoclonal antibodies against human platelet membrane glycoprotein IIIa (GPIIIa) were obtained. One monoclonal antibody, designated as 1B1, was found to inhibit both collagen-induced platelet aggregation and release reactions. This antibody also inhibited the binding of 125I-labeled collagen to human platelets. On the other hand, the other antibody, designated as B10, had no effect on platelet activation induced by a number of physiological stimulants including collagen. Direct binding studies involving 125I-labeled 1B1 or B10 demonstrated that the binding sites for these antibodies on unstimulated platelets have dissociation constants of 4.2 and 14.0 nM, respectively. The binding of 125I-labeled 1B1 or B10 to platelets was not inhibited by the other antibody. Purified 1B1 and B10 were covalently coupled to Affi-Gel and then proteolytic fragments of GPIIIa were applied to the Affi-Gel immunoadsorbent columns. Of the several proteolytic fragments, the 56 kilodaltons (kDa) fragment obtained on digestion with V8 protease bound to both of the columns. The 69 and 55 kDa fragments obtained with BrCN bound to only the 1B1 Affi-Gel column, while the 63 kDa fragment obtained with chymotrypsin only bound to the B10-Affi-Gel column. Based on the partial amino acid sequences of these fragments and the amino acid sequence of GPIIIa (C. A. Fitzgerald, B. Steiner, S. C. Rall, Jr., S. Lo and D. R. Phillips, J. Biol. Chem., 262, 3936 (1987), the epitopes for 1B1 and B10 were concluded to be located at amino acids 335 to 582 and 206 to 335, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Monoclonal antibodies against human platelet membrane glycoprotein IIIa and collagen-induced platelet activation. 274 83

The authors isolated a product of proteolytic degradation of glycoprotein IIIa (GPIIIa) which is formed on the surface of human platelets during incubation with chymotrypsin and which was previously described as the 66 kDa platelet membrane component. This component migrated with an apparent Mr 62,400 in a non-reduced system of sodium dodecyl sulfate polyacrylamide gel electrophoresis. In a reduced system it yielded two major subunits migrating with apparent Mr 14,000-17,000 and 65,000. The low-molecular weight component began with the NH2-terminal sequence of GPIIIa (GPNICTTR...) and the larger component with residue 348 of GPIIIa (GKIRSKKA...) as deduced from a cDNA clone of this glycoprotein. The two subunits appeared to be linked by one or more S-S bridges supporting the contention that GPIIIa is a highly folded molecule on the platelet membrane. In contrast to GPIIIa, the '66 kDa component' did not bind to GRGDSPK-agarose, to fibrinogen-agarose nor to insolubilized monoclonal antibody recognizing the GPIIb/IIIa complex. The exposure of fibrinogen receptors during the course of incubation of platelets with chymotrypsin preceded the formation of the '66 kDa component' characterized in this study. An intermediate product of GPIIIa proteolysis migrating with an apparent Mr 120,000 in a non-reduced system and Mr 80,000 in a reduced system was identified as a precursor of the '66 kDa component'. The '120 kDa component' was not retained on GRGDSPK-agarose or on fibrinogen-agarose but it was retained on insolubilized antibody recognizing the GPIIb/IIIa complex. Incubation of platelets with porcine pancreatic elastase or human granulocytic elastase resulted in the formation of similar proteolytic degradation fragments.
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PMID:Structural and functional characterization of major platelet membrane components derived by limited proteolysis of glycoprotein IIIa. 275 53

Platelets of a patient with Friedreich's ataxia have been investigated because of a codiagnosis of thrombasthenia. No aggregation occurred in response to adenosine diphosphate, platelet activating factor-acether, a stimulatory antiplatelet monoclonal antibody, or phorbol myristate acetate, although platelet aggregation could be induced with thrombin, the calcium ionophore A23187, or high concentrations of collagen. Shape change, adenosine triphosphate secretion, and the responses of the platelets' protein phosphorylation systems to all agonists were normal. Immunologic analysis of the patient's radiolabeled platelet surface proteins revealed normal levels of glycoproteins IIB and IIIa. However, no iodine 125-fibrinogen binding occurred after stimulation of the patient's platelets with adenosine diphosphate. In contrast, pretreatment of the patient's platelets with the proteolytic enzyme alpha-chymotrypsin resulted in the exposure of active 125I-fibrinogen binding sites. The patient's platelets exhibited normal aggregation to fibrinogen after their pretreatment with chymotrypsin and with elastases derived either from porcine pancreas or from human granulocytes. A murine monoclonal antibody directed against the human platelet membrane glycoproteins IIb and IIIa calcium-dependent epitope and rabbit polyclonal anti-human platelet membrane and human anti-P1A1 antibodies immunoprecipitated glycoproteins IIb and IIIa and a 66 kd cleavage product of glycoprotein IIIa from sodium dodecyl sulfate-Triton X-100 extracts of the patient's proteolytically treated platelets. The patient appears to exhibit a unique type of thrombopathy involving a defect in the exposure of fibrinogen receptors. The association between the neurologic disorder and the platelet defect is still unclear.
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PMID:Identification of a unique type of thrombopathy of human platelets: defect in the exposure of active fibrinogen receptors in a patient with Friedreich's ataxia. 283 36

Incubation of platelets with chymotryptin leads to the exposure of fibrinogen receptors and to the appearance of a 66 kDa membrane component on the surface of platelets. Both glycoprotein IIIa (GP IIIa) and a 66 kDa component were precipitated from detergent extracts of solubilized, surface radiolabeled chymotrypsin-treated platelets by human anti-PlAl antisera. Moreover, the presence of the P1A1 antigen was identified on GP IIIa (but not on GP IIb) and on a 66 kDa protein by means of immunoblot procedures using platelet Triton X-114 extracts and these purified proteins. Anti-PlAl antiserum did not recognize GP IIIa on the surface of intact (untreated) platelets nor the 66 kDa protein on the surface of chymotrypsin-treated platelets of PlAl-negative individuals. The present data demonstrate directly that the 66 kDa protein is derived from GP IIIa and contains the PlAl alloantigen.
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PMID:Identification of PlAl alloantigen domain on a 66 kDa protein derived from glycoprotein IIIa of human platelets. 299 25

Previous experiments demonstrated that chymotrypsin, but not adenosine diphosphate (ADP), exposed fibrinogen binding sites on platelets from patients with Glanzmann's thrombasthenia. Three of these patients have been reexamined, and previous observations were confirmed. The quantity of iodine 125-labeled glycoprotein IIb (GPIIb) and glycoprotein IIIa (GPIIIa) on the platelets of these patients was considerably less than normal but was detectable by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and autoradiography. The amount of residual GPIIb and GPIIIa as measured by binding studies with radiolabeled monoclonal antibodies was between 3% and 12% of the normal value. Platelet suspensions from these patients did not aggregate with fibrinogen and did not bind 125I-fibrinogen on stimulation with ADP. However, incubation of these platelets with chymotrypsin or pronase resulted in fibrinogen binding and platelet aggregation. Monoclonal antibodies specific for the GPIIb-GPIIIa complex blocked both the fibrinogen binding and the aggregation of enzyme-treated platelets. The treatment of washed platelets of a fourth thrombasthenic patient with ADP or with chymotrypsin failed to result in fibrinogen binding and aggregation. However, the level of GPIIb and GPIIIa on these platelets as measured by a Western blot technique and by monoclonal antibody binding amounted to less than 0.35% to 0.5% of normal values. In conclusion, fibrinogen binding sites exposed on thrombasthenic platelets by chymotrypsin are derived from GPIIb-GPIIIa molecules. Aggregation of chymotrypsin-treated thrombasthenic platelets by fibrinogen appears to represent a sensitive test for detection of functionally active GPIIb-GPIIIa complex on the platelet surface.
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PMID:Aggregation of chymotrypsin-treated thrombasthenic platelets is mediated by fibrinogen binding to glycoproteins IIb and IIIa. 299 74

The glycoprotein (GP) localization of a new platelet-specific allo-antigen Yukb is described. The antibody was isolated from serum of a patient with neonatal allo-immune thrombocytopenia. In immunoblot procedure, it bound exclusively to platelet GP IIIa, like anti-PlA1, while the known anti-Baka and anti-Leka reacted with GP IIb. Analysis of GP from chymotrypsin-treated platelets with anti-Yukb revealed no binding in the 68-kilodalton position while anti-PlA1 did. Thus, unlike the PlA1 antigen, the Yukb determinant either resides on the 30-kilodalton fragment of GP IIIa or it is destroyed by chymotrypsin treatment.
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PMID:Identification of the Yukb allo-antigen on platelet glycoprotein IIIa. 366 Jul 69

We report the immunochemical characterization of a new platelet-specific alloantigen detected using an IgG antibody isolated from the serum of a patient with posttransfusion purpura (PTP). In indirect immunoprecipitation experiments, the antibody, termed anti-Leka, predominantly precipitated glycoprotein (GP) IIb from Triton X-100 lysates of normal human platelets. In an immunoblot procedure, which involved the transfer of platelet polypeptides separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to nitrocellulose membrane, anti-Leka bound exclusively to GP IIb. Under identical conditions, four anti-PlA1 antibodies each reacted with GP IIIa. No binding of anti-Leka IgG occurred to Leka (-) platelets or to their separated polypeptides although GP IIb was normally detected by Coomassie blue staining. After electrophoresis of reduced platelet proteins, the Leka determinant was localized to the IIb alpha chain. Thus, unlike the PlA1 antigen, the Leka determinant was not destroyed by disulfide reduction. Analysis of platelets from a patient with Glanzmann's thrombasthenia revealed little or no binding in the GP IIb position. Anti-Leka permitted the identification of 76,000 and 60,000 dalton fragments of GP IIb retained by the platelet following chymotrypsin treatment. Our results further highlight the immunogenicity of the GP IIb-IIIa complex. They also suggest that antibodies against GP IIb can cause the thrombocytopenia observed in PTP and that anti-PlA1 antibodies do not account exclusively for the pathophysiology of this immune disorder.
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PMID:Immunochemical characterization of the platelet-specific alloantigen Leka: a comparative study with the PlA1 alloantigen. 620 52

In summary: Incubation of platelets with ADP or proteolytic enzymes (chymotrypsin or pronase) results in an exposure of two classes of specific binding sites on platelet surface: low and high affinity fibrinogen receptors. Fibrinogen interaction with these receptors results in platelet aggregation. High affinity fibrinogen receptors are not exposed on thrombasthenic platelets stimulated by ADP but are rendered available on chymotrypsin-treated thrombasthenic platelets; low affinity receptors cannot be exposed by ADP or chymotrypsin on these platelets. Availability of high affinity fibrinogen receptors on thrombasthenic platelets may depend on the residual glycoprotein IIIa. Fibrinogen receptors appear to be associated with glycoproteins IIb, IIIa and a 66,000 Mr platelet membrane component that is exposed during proteolysis of platelet membranes. Some of the platelet-binding sites on the fibrinogen molecule appear to be associated with the COOH-terminal portion of the gamma chain (gamma 374-411). Additional binding sites may also be located in the COOH-terminal portion of the A alpha chain. The conformation of the fibrinogen molecule may be important in its interaction with platelets. Platelet aggregation may result from bridging platelets by fibrinogen molecule in the presence of bivalent cations. In conclusion, platelet interaction with fibrinogen is a complex process involving different binding sites of the fibrinogen molecule. Our own data and review of literature suggest that platelet-interaction with fibrinogen is of major significance in hemostasis.
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PMID:Fibrinogen interaction with platelet receptors. 630 5


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