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:3.4.21.4 (trypsin)
42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The fine structure, protein composition, and roles in flagellar movement of specific axonemal components were studied in wild-type Chlamydomonas and paralyzed mutants pf-14, pf-15A, and pf-19. Electron microscope examination of the isolated axoneme of pf-14 showed that it lacks the radial spokes but is otherwise structurally normal. Comparison of isolated axonemes of wild type and pf-14 by sodium dodecyl sulfate-acrylamide gel electrophoresis indicated that the mutant is missing a protein of 118,000 mol wt; this protein is apparently a major component of the spokes. Pf-15A and pf-19 lack the central tubules and sheath; axonemes of these mutants are missing three high molecular weight proteins which are probably components of the central tubule-central sheath complex. Under conditions where wild-type axonemes reactivated, axonemes of the three mutants remained intact but did not form bends. However, mutant and wild-type axonemes underwent identical adenosine triphosphate-induced disintegration after treatment with trypsin; the dynein arms of the mutants are therefore capable of generating interdoublet shearing forces. These findings indicated that both the radial spokes and the central tubule-central sheath complex are essential for conversion of interdoublet sliding into axonemal bending. Moreover, because axonemes of pf-14 remained intact under reactivating conditions, the nexin links alone are sufficient to limit the amount of interdoublet sliding that occurs. The axial periodicities of the central sheath, dynein arms, radial spokes, and nexin links of Chlamydomonas were determined by electron microscopy using the lattice-spacing of crystalline catalase as an internal standard. Some new ultrastructural details of the components are described.
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PMID:Chlamydomonas flagellar mutants lacking radial spokes and central tubules. Structure, composition, and function of specific axonemal components. 63 25

The amyloid protein precursor (APP) of Alzheimer's disease was found to bind saturably (Kd = 60 nM) to embryonic chick brain extracellular matrix (ECM). The binding of APP to ECM was not inhibited by 10 micrograms/ml heparin or heparan sulfate. However, pretreatment of cells with 1 mM 4-methylumbelliferyl-beta-D-xyloside, an inhibitor of proteoglycan biosynthesis, reduced the number of APP binding sites on the ECM by 80%. The binding of APP to ECM was also inhibited by pretreatment with chlorate, an inhibitor of glycan sulfation, and heparitinase, which digests the carbohydrate component of heparan sulfate proteoglycans. These results suggest that APP binds with high affinity to one or more heparan sulfate proteoglycans. Acidic and basic fibroblasts growth factor (FGF) also bound to chick ECM. When ECM was incubated with a protease associated with the enzyme AChE (AChE-AP), APP and acidic FGF were released intact from the matrix. The AChE-AP was at least 100-fold more potent in releasing APP from ECM than other trypsin-like proteases (trypsin, plasmin, thrombin). The action of the AChE-AP was inhibited by glia-derived nexin (protease nexin I) and by human brain APP at low nanomolar concentrations. These results suggest that in vivo an AChE-AP may cleave ECM proteins to regulate the availability of soluble APP or other factors bound to the ECM.
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PMID:Association and release of the amyloid protein precursor of Alzheimer's disease from chick brain extracellular matrix. 127 36

The protease inhibitor, protease nexin-2 (PN-2), is the secreted isoform of the Alzheimer's amyloid beta-protein precursor (A beta PP) that contains the Kunitz-type protease inhibitor (KPI) domain. Here we describe the use of the methylotrophic industrial yeast Pichia pastoris as a host system for the large scale production of the KPI domain of PN-2/A beta PP. In addition to the 57 amino acid KPI domain, the expression product contained an additional four amino acid residues at its amino terminus that correspond to amino acids 285-288 of A beta PP (Ponte et al. 1988 Nature 311:525-527). This expression system generated yields of greater than 1.0 gram of KPI domain per liter of fermentation media. The secreted 61 amino acid product was purified to homogeneity and biochemically characterized. Amino acid analysis and sequencing of the entire expressed KPI domain verified its integrity. Similar to native PN-2/A beta PP, the purified KPI domain potently inhibited trypsin, chymotrypsin, and coagulation factor XIa. Although heparin augments the inhibition of factor XIa by native PN-2/A beta PP it had no effect on the inhibition of factor XIa by expressed KPI domain suggesting that heparin binds to regions on native PN-2/A beta PP outside of the protease inhibitory domain. This KPI domain expression product should be useful in studying the physiologic and pathophysiologic functions of PN-2/A beta PP.
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PMID:High level expression, purification, and characterization of the Kunitz-type protease inhibitor domain of protease nexin-2/amyloid beta-protein precursor. 149 47

When cultured astroglia are treated with agents that elevate intracellular cyclic AMP, they become process-bearing stellate cells and resemble differentiated astrocytes in vivo. Thrombin rapidly reversed the stellation induced by dibutyryl cyclic AMP, forskolin, or isoproterenol in cultured rat astrocytes; half-maximal and maximal effects occurred at 0.5 and 8 pM, respectively. The proteolytic activity of thrombin was required for stellation reversal, as thrombin derivatized at its catalytic site serine with a diisopropylphospho group was inactive. Two thrombin inhibitors, protease nexin-1 and hirudin, blocked and reversed the effect of thrombin. The stellation reversal effect of thrombin was specific, as 300-1,000-fold higher concentrations of other serine proteinases, including plasmin, urokinase, trypsin, and T cell serine proteinase-1, were ineffective. Thrombin is a mitogen for astrocytes at concentrations in excess of 30 pM. Thrombin increased both cell number and ornithine decarboxylase activity, an early marker for mitogenic stimulation, in astrocyte cultures. The lowest thrombin concentrations that completely reversed astrocyte stellation, however, did not increase ornithine decarboxylase activity. Moreover, several other mitogens for astrocytes did not reverse dibutyryl cyclic AMP-induced stellation. Thus, the stellation reversal effect of thrombin is distinct from the mitogenic response.
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PMID:Reciprocal modulation of astrocyte stellation by thrombin and protease nexin-1. 169 Dec 80

Interaction of vitronectin with glia-derived nexin (GDN), thrombin, and the complex GDN-thrombin was demonstrated in direct binding assays that indicated the formation of binary and ternary complexes. The concentration of vitronectin necessary to obtain 50% saturation of the immobilized GDN-thrombin complex binding sites (EC50) was about 1 nM. Under similar experimental conditions, the EC50 of vitronectin for the immobilized antithrombin-III-thrombin complex was about fivefold higher. A tight complex was also formed between vitronectin and immobilized GDN (EC50 approximately 1.5 nM) but when vitronectin was immobilized, GDN displayed a reduced affinity for vitronectin (EC50 approximately 10 nM). These results suggest differences between the immobilized and free conformations of GDN and/or vitronectin. In contrast, vitronectin displayed negligible affinity for antithrombin III. Biotinylated GDN was used to characterize further the binding of GDN or the GDN-thrombin complex to vitronectin. The interaction of the biotinylated GDN-thrombin complex with immobilized vitronectin (EC50 approximately 2 nM) was completely blocked by nonbiotinylated complexes of thrombin with either GDN or antithrombin III, whereas free GDN, free thrombin and the GDN-trypsin complex were only weak competitors. Active-site-blocked urokinase and the complex GDN-urokinase also strongly competed for binding of the biotinylated GDN-thrombin complex to vitronectin. Binding of biotinylated GDN to immobilized vitronectin was specific, saturable and was competed with decreasing efficiency by the GDN-thrombin complex, free GDN and free antithrombin III. These interactions between the adhesive component vitronectin and the serine protease inhibitor GDN may relate to localized control of thrombin and/or urokinase action at certain extravascular sites. These results are discussed in terms of binding sites for vitronectin on GDN, thrombin, and the GDN-thrombin complex.
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PMID:Specific interaction of vitronectin with the cell-secreted protease inhibitor glia-derived nexin and its thrombin complex. 169 27

A low molecular weight platelet inhibitor of factor XIa (PIXI) has been purified 250-fold from releasates of washed and stimulated human platelets. Molecular weight estimates of 8400 and 8500 were determined by gel filtration and SDS-polyacrylamide gel electrophoresis, respectively, although a second band of Mr 5000 was present upon electrophoresis. The inhibitor does not appear to be one of the platelet-specific, heparin-binding proteins, since it neither bound to nor was affected by heparin. An amount of PIXI which inhibited by 50% factor XIa cleavage of the chromogenic substrate S2366 (Pyr-Glu-Pro-Arg-pNA-2H2O) only slightly inhibited (5-9%) factor XIIa, plasma kallikrein, plasmin, and activated protein C and did not inhibit factor Xa, thrombin, tPA, or trypsin, suggesting specificity for factor XIa. Kinetic analyses of the effect of PIXI on factor XIa activity demonstrated mixed-type, noncompetitive inhibition of S2366 cleavage and of factor IX activation with Ki's of 7 x 10(-8) and 3.8 x 10(-9) M, respectively. Immunoblot analysis showed that PIXI is not the inhibitory domain of protease nexin II, a potent inhibitor of factor XIa also secreted from platelets. Amino acid analysis showed that PIXI has no cysteine residues and, therefore, is not a Kunitz-type inhibitor. PIXI can prevent stable complex formation between alpha 1-protease inhibitor and factor XIa light chain as demonstrated by SDS-polyacrylamide gel electrophoresis. The inhibition by PIXI of factor XIa-catalyzed activation of factor IX and its capacity to prevent factor XIa inactivation by alpha 1-protease inhibitor, combined with the specificity of PIXI for factor XIa among serine proteases found in blood, suggest a role for PIXI in the regulation of intrinsic coagulation.
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PMID:A low molecular weight platelet inhibitor of factor XIa: purification, characterization, and possible role in blood coagulation. 173 24

The purpose of this study was to determine the effect of chemical modification of lysyl residues on thrombin interaction with platelet membrane proteins. Modification of lysyl residues by pyridoxal-5'-phosphate affected two different sites on thrombin and resulted in a greatly decreased binding to platelets. Using a crosslinking bifunctional reagent [bis(sulphosuccinimidyl) suberate (BS3)], we show that modified thrombin retained the ability to form high molecular mass (greater than or equal to 400 kDa) complexes with yet unidentified platelet proteins and to bind to platelet protease nexin I, but had lost the ability to bind to platelet glycoprotein Ib (GPIb). As previously reported by others, heparin protected one of the two sites from phosphopyridoxylation. In contrast modified thrombin, heparin-protected modified thrombin retained the ability to bind to GPIb, indicating that the lysyl residue(s) protected by heparin from the modification are essential for GPIb binding. While unprotected modified thrombin failed to bind hirudin, heparin-protected modified thrombin retained its ability to bind the carboxy-terminal hirudin peptide H54-65. Tritium-labelling of the modified lysyl residues and degradation of modified thrombins by CNBr or trypsin confirmed that the lysyl residue(s) protected by heparin and essential for GPIb binding are located in the thrombin binding domain for the carboxyl-terminal tail of hirudin, within the sequence 18-73 of the thrombin B chain.
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PMID:Effect of phosphopyridoxylation on thrombin interaction with platelet glycoprotein Ib. 176 65

Structural and functional properties of alpha-protease nexin I (alpha-PNI) expressed in Chinese hamster ovary cells were studied. All three cysteines were in the reduced form, showing that the potential disulfide bridge between residues Cys117 and Cys131 was not formed. Heparin association rate enhancements were from ka = 8.3 x 10(5) to 0.7-1.6 x 10(9) M-1 s-1 for the interaction of PNI with thrombin, from ka = 5.1 x 10(3) to 3.5 x 10(5) M-1 s-1 for interaction with Factor Xa, and from ka = 2.2 x 10(6) to 1.0 x 10(7) M-1 s-1 for interaction with trypsin; there was no rate enhancement of the plasmin interaction (ka = 1.0 x 10(5) M-1 s-1). The minimal heparin pentasaccharide had no effect on these interactions. Cleavage of the reactive center loop of PNI by three different proteases gave the typical stressed to relaxed change in thermal stability, but unlike with antithrombin III, there was no loss of heparin affinity. A similar difference from antithrombin was that PNI-thrombin complexes retained normal heparin affinity. These results are compatible with a role for protease nexin I as a cell-associated thrombin inhibitor that remains bound to the cell surface even after complexing with the protease, as compared with the role of antithrombin III as a circulating inhibitor of thrombin that becomes activated on binding to the microvasculature and is released on complex formation.
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PMID:Protease specificity and heparin binding and activation of recombinant protease nexin I. 193 53

Three alternatively spliced forms of the amyloid precursor protein (APP), APP-695, APP-751, and APP-770, were expressed in the baculovirus expression vector system. The recombinant proteins were secreted into the culture medium by infected insect cells, and APP molecules were detected in insect cells and medium 2 days after infection with the recombinant APP-baculoviruses. A partial sequence of the NH2 terminus of the secreted protein revealed identity with the native secreted protein and showed that the signal peptide was recognized and properly cleaved in insect cells. Purified secreted recombinant APP-751 comigrated with protease nexin 2 purified from platelets and fibroblasts. A 15-kDa COOH-terminal fragment of APP was also detected in cells infected with recombinant baculoviruses, suggesting that recombinant APP proteins were cleaved at the COOH-terminal end like native APP protein. Recombinant APP-751 and APP-770 formed complexes with epidermal growth factor-binding protein, whereas APP-695 did not. In addition, recombinant APP-751 and APP-770 inhibited trypsin and chymotrypsin activity, whereas APP-695 did not. Growth of a human fibroblast cell line, A-1, that required APP for complete growth, was restored upon addition of secreted recombinant APP-695 or APP-751. Thus, the appropriately sized, secreted recombinant APP proteins produced in this expression system are biologically active.
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PMID:Expression of active secreted forms of human amyloid beta-protein precursor by recombinant baculovirus-infected insect cells. 194 49

The addition of two synthetic peptides with antiprotease activity to the culture medium of mouse neuroblastoma cells results in the promotion of neurite outgrowth. One of these peptides has a sequence corresponding to the reactive center of protease nexin-1 and inhibits both trypsin and thrombin. Its effect on neuroblastoma cells is similar to that found on serum withdrawal from the culture medium, giving rise to cells with one or two long neurites, and is reversed upon the addition of thrombin to the culture medium. The sequence of the other peptide is present in one of the precursor proteins of the main component of the amyloid plaques of Alzheimer's disease patients' brains, and corresponds to protease nexin-2. It can inhibit trypsin but fails to inhibit thrombin at low doses. Its effect on neuroblastoma cells is slightly different from that observed after serum deprivation, as a significant proportion of stellate cells, with short and branched neurites, is observed. An increase in the phosphorylation of microtubule-associated protein MAP-1B, which accompanies neurite outgrowth induced by serum deprivation, is also observed upon addition of the two antiprotease synthetic peptides, although the nexin-2 (amyloid) peptide induces a less marked increase in phosphorylated MAP-1B than does the nexin-1 peptide. These results may be correlated with the different antiprotease activities of both synthetic peptides, thus suggesting a role for a balance between trypsin-like and thrombin-like proteases and their inhibitors in eliciting neurite outgrowth under normal and pathological conditions.
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PMID:Addition of protease inhibitors to culture medium of neuroblastoma cells induces both neurite outgrowth and phosphorylation of microtubule-associated protein MAP-1B. 205 67


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