Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An assay system for protein C (PC) activity and PC-inhibitor in plasma was developed. The assay was based on: (1) binding of PC to wells of a microtiter plate coated with a murine monoclonal anti-PC antibody (C3) that did not interfere with the activity or activation of PC; (2) activation of immobilized PC with Protac C; (3) incubation with or without a source of activated PC inhibitor; and (4) measurement of amidolytic activity using the substrate S-2366. The activity assay was specific for PC and sensitive to less than 1 microliter of plasma or 4 ng PC. Inhibition of activated PC by plasma followed pseudo first order kinetics. Heparin caused a dose dependent increase in the inhibition rate with half maximal stimulation at approximately 3 U/ml and maximal stimulation at heparin concentrations greater than or equal to 10 U/ml. This assay is suitable not only for determination of functional plasma levels of PC and PC inhibitor activities but also for kinetic studies of inhibition of activated PC in complex systems, such as plasma. Studies showed that urokinase interfered with the inhibition of APC by plasma inhibitor(s).
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PMID:Functional assays for protein C activity and protein C inhibitor activity in plasma. 254 80

Tryptase (EC 3.4.21.59), the major secretory product of human mast cells, has become widely used as a biochemical marker for mast cells and mast cell activation, and is attracting attention as a mediator of allergic disease. However, there is little information available on the properties, or even the presence, of this protease in commonly used species of laboratory animals. We, here, report the demonstration and characterisation of this enzyme in the guinea pig lung. Tryptic activity resistant to alpha 1-proteinase inhibitor and soybean trypsin inhibitor was detected in sections of guinea pig lung tissue with the histochemical substrate Z-Gly-Pro-Arg-MNA. It was localised to mast cells and appeared to be present in all mast cells staining with Alcian Blue. A tryptic protease was purified 2400-fold from whole lung tissue by high salt extraction, cetylpyridinium chloride precipitation, heparin agarose chromatography, and gel filtration. This enzyme was found to be multimeric with a subunit of 38 kDa and a native molecular mass of 860 +/- 100 kDa. Inhibitor studies identified it as a serine protease. Like human tryptase, it was inhibited by leupeptin, benzamidine, and APC 366 (N-(1-hydroxy-2- naphthoyl)-L-arginyl(-L-prolinamide hydrochloride), but not by alpha 1-proteinase inhibitor, soybean trypsin inhibitor, or antithrombin III. Its response to changes in pH and ionic strength was similar to that of human tryptase. Differences between the guinea pig and human enzymes were seen in activity toward a panel fo 10 tryptic p_nitroanilide peptide substrates. Kinetic constants were determined for two of these: with L-Pyr-Pro-Arg-pNA the guinea pig tryptase had a similar Km but a 5-fold lower kcat than human tryptase, and with L-Pyr-Gly-Arg-pNA the guinea pig enzyme had a 10-fold lower Km and a 30% greater kcat than human counterpart. Heparin stabilised guinea pig tryptase, but did not alter its kinetic parameters as it did with human tryptase, decreasing the Km towards both substrates. The presence of a protease with similarities to human tryptase in the mast cells of guinea pigs suggests that this species may be an appropriate model to investigate the actions to tryptase in vivo, provided cognizance is taken of the differences that do exist.
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PMID:Guinea pig lung tryptase. Localisation to mast cells and characterisation of the partially purified enzyme. 869 58

Protein C is the zymogen of an anticoagulant serine protease and is converted to its active form (activated protein C: APC) by thrombin in the presence of thrombomodulin. APC plays an important role in regulating coagulation and fibrinolysis by inactivating not only blood coagulation factors Va and VIIIa but also type-1 plasminogen activator inhibitor (PAI-1). The aim of the present study was to examine the effect of a human APC product (designated as CTC-111), compared with that of heparin, on the disseminated intravascular coagulation (DIC) induced by lipopolysaccharide (LPS) in rats. LPS (1 mg/kg/h) infusion was performed through a femoral vein for 4 h. One-fifth amount of the total dosage of CTC-111 or heparin was injected into the other femoral vein, followed by a 4-h infusion of the remainder. Both CTC-111 (10,000-100,000 U/kg) and heparin (400-800 IU/kg) inhibited the decrease in platelet count and fibrinogen level equally. The prolonged activated partial thromboplastin time and prothrombin time observed in DIC rats were further elongated in both CTC-111- and heparin-treated rats. But, this prolongation was less in CTC-111-treated rats than in the heparin-treated ones. Heparin inhibited the increase in fibrin and fibrinogen degradation products more prominently than CTC-111. On the other hand, CTC-111 strongly inhibited the increase in PAI-1 activity but heparin did not. These results suggest that CTC-111 may enhance fibrinolysis through its direct inhibitory effect on PAI-1. The parameters for liver or renal damage, i.e., plasma glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (GPT), creatinine (Cre) and blood urea nitrogen (BUN), were significantly increased by LPS infusion. Both CTC-111 (100,000 U/kg) and heparin (800 IU/kg) decreased the increase in GOT and GPT levels significantly, whereas neither affected the increase in Cre or BUN. From these results, the activation of the blood coagulation system might partially contribute to the progression of liver damage caused by LPS, and might be less involved in the progression of renal damage in this model. In conclusion, CTC-111 showed both anticoagulant and profibrinolytic activity in the LPS-induced DIC model without excessive prolongation of coagulation time. From these results, CTC-111 is expected to be a useful remedy for DIC without the risk of bleeding.
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PMID:Effect of activated human protein C on disseminated intravascular coagulation induced by lipopolysaccharide in rats. 1105 Jun 97

Protein C in its activated form (APC) limits thrombin generation. Protein C inhibitor (PCI) readily neutralizes APC. Heparin accelerates this reaction, which may complicate anticoagulant treatment in patients with varying APC generation potential. A potent anticoagulant conjugate of antithrombin and heparin (ATH) was prepared, and its effect on APC+PCI reactions was tested. Second order rate constants for APC+PCI reactions were measured by discontinuous rate experiments in the presence of heparin or ATH. Similarly, low molecular weight fractions of heparin (LMWH) and ATH (LMWATH) were tested, as was high molecular weight ATH (HMWATH). Mechanisms of heparin or ATH binding to APC or PCI were assessed using electrophoresis. While heparin gave a higher maximal APC inhibition rate compared to ATH, peak inhibition rate was achieved at comparatively lower ATH concentrations. Since LMWH was ineffective at enhancing APC inhibition by PCI, unfractionated heparin likely acts by bridging APC and PCI. Unlike heparin, ATH may conformationally activate either APC or PCI since LMWATH significantly catalyses APC inhibition. Binding studies showed that ATH readily associates with APC. Thus, although a small fraction of ATH efficiently catalyses APC inhibition by PCI, complete ATH preparations induce a decreased maximal rate of APC-PCI formation compared to unfractionated heparin.
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PMID:Effect of covalent antithrombin-heparin on activated protein C inactivation by protein C inhibitor. 2053 15