Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Tissue-type plasminogen activator (t-PA), the serine protease responsible for catalyzing the production of plasmin from plasminogen at the site of blood clots, is synthesized as a single-chain polypeptide precursor. Proteolytic cleavage at the C-terminal side of Arg275 generates a two-chain form of the enzyme whose subunits are held together by a single disulfide bond. We have measured the activities of both forms of the wild-type enzyme, as well as that of a mutant enzyme (Arg275----Gly), created by oligonucleotide-directed mutagenesis, that cannot be cleaved into a two-chain form. Both types of single-chain t-PAs are enzymatically active and exhibit identical Vmax and Km values when assayed with synthetic peptide substrates, indicating that the single amino acid change had no effect on the amidolytic activity of the enzyme. However, cleavage of wild-type t-PA into the two-chain form results in increased activity both on a peptide substrate and on the natural substrates Lys- and Glu-plasminogen in the absence or presence of stimulation by soluble fibrin. The enhanced activity is due to a 3-5-fold increase in the Vmax of the cleaved enzyme, rather than to any change in the Km values for the various substrates. During incubation with plasminogen, the single-chain form of wild-type t-PA is converted to the two-chain form by plasmin generated during the reaction. This conversion, from the less active form of the enzyme, results in a reaction that displays biphasic kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:The single-chain form of tissue-type plasminogen activator has catalytic activity: studies with a mutant enzyme that lacks the cleavage site. 249 49

Tissue-type plasminogen activator (t-PA), an important component of the fibrinolytic system, is now available as a biotechnologically manufactured recombinant protein for therapeutic use. It has proved highly effective in the clinical therapy of acute thromboembolic diseases such as myocardial infarction and pulmonary embolism. t-PA activates plasminogen to plasmin, which subsequently dissolves the fibrin network of a blood clot. This activation by t-PA occurs selectively on the clot surface, with negligible systemic side effects. The half-life of t-PA in vivo is in the order of minutes due to rapid hepatic elimination. t-PA is a glycoprotein with serine protease activity and consists of a polypeptide chain with 527 amino acids. Recently, intensive research efforts have been devoted to modification of the molecular structure of t-PA, with the objective of further increasing fibrin specificity and catalytic activity, or reducing the rate of elimination. As a result, considerable insights into structure-function relationships within the t-PA molecule have been gained, but as yet no clinically utilizable variant has been constructed which is in all respects superior to naturally occurring t-PA.
 ...
PMID:Properties of molecular variants of tissue-type plasminogen activator. 250 92

Laminin and fibronectin are glycoproteins that influence cell behavior and mediate cell/substratum adhesion. We have examined the interaction of these macromolecules with the serine protease plasminogen activator (PA) in two types of extracellular matrices; one produced by the murine Engelbreth-Holm-Swarm (EHS) tumor (Matrigel), and another by normal kidney epithelial cells in culture. Matrigel was found to contain significant quantities of tissue-type PA (tPA). Two of the major components of Matrigel, laminin and type IV collagen, were also examined. Tissue-type PA was associated with purified preparations of laminin; however, it was not found associated with type IV collagen. Normal kidney epithelial cells in culture secrete large amounts of urokinase (UK) and deposit a subepithelial matrix containing both laminin and fibronectin. These matrix macromolecules were isolated from the deposited matrix by immunoprecipitation, examined by zymography, and found to contain UK. The potential role of this interaction in the mechanisms of cell migration and matrix remodeling is discussed.
 ...
PMID:The interaction of plasminogen activator with a reconstituted basement membrane matrix and extracellular macromolecules produced by cultured epithelial cells. 250 31

Extravascular participation of the serine protease plasminogen activator (PA) in tissue remodelling and cell migration may be relevant in the regulation of periodontal homeostasis and the pathogenesis of periodontal disease. The molecular nature of authentic PA in crevicular fluid has been characterized, and this study has sought to determine whether human supragingival plaque also contains PA; if so, of which molecular species and from what source. Thirty samples of supragingival plaque plaque from 10 individuals, extensively washed to remove adherent saliva, were all found by substrate analysis to have tissue-type PA (tPA) activity. Unstimulated parotid or mixed saliva also showed tPA activity, but submandibular saliva had no measurable PA activity. Freshly isolated plaque microbes cultured under aerobic or anaerobic conditions contained no PA activity (preliminary investigation). PA activity was restricted to individual epithelial cells suggesting that the origin of PA activity in human supragingival plaque is in part from plaque-adherent epithelial cells.
 ...
PMID:Molecular characterization of plasminogen activator in human supragingival plaque. 250 47

Sympathetic neurons release both urokinase plasminogen activator (uPA) and tissue plasminogen activator (tPA). A number of inhibitors of serine proteases have been tested to determine their effects on neurite outgrowth from rat sympathetic neurons. Some inhibitors increase neurite outgrowth while others have little or no effect on outgrowth. Inhibition of plasminogen activator (PA) activity but not other serine protease activity correlates with the increase in neurite outgrowth (uPA, r = 0.89; tPA, r = 0.86; plasmin, r = 0.015; thrombin, r = 0.025). Antibodies that inhibit uPA activity increase neurite outgrowth, while antibodies that bind to uPA but do not inhibit activity do not alter outgrowth. Time-lapse videomicroscopy of neurite outgrowth indicates that about 85% of the neurites increase their rate of outgrowth following exposure to inhibitors of PA. Routinely, 1-2 min after exposure of a growth cone to an inhibitor, there is an increase in lamellipodial activity at the leading edge of the growth cone and a decrease in lamellipodial activity on the sides and base of the growth cone. The increase in the rate of outgrowth combined with the decrease in lamellipodial activity on the sides of the growth cones results in neurites being very long and straight in the presence of inhibitors (persistence time P = 3.7 and 15.3 hr for controls and in the presence of inhibitors of PA, respectively). PAs released from sympathetic neurons and PC12 cells interact with 3 different binding sites on the cell surface: (1) an inhibitor of serine proteases (including uPA and tPA) is bound to the surface via a heparinase-sensitive site; (2) a uPA-selective binding site is present in patches on the bottom surface of PC12 cells; and (3) a tPA-selective binding site with high affinity (KD = 23 +/- 10 nM) and high capacity (340,000 +/- 130,000 sites/neuron) for 125I-tPA is homogeneously distributed over the entire surface. Data in the present study are consistent with PA being involved in neurite outgrowth and open the possibility of other PA-dependent functions occurring when tPA and/or uPA interacts with cell surface binding sites.
 ...
PMID:Neuronal plasminogen activators: cell surface binding sites and involvement in neurite outgrowth. 251 75

Catalytic activity of tissue-type plasminogen activator (t-PA) in plasma is regulated in part by formation of complexes with specific inhibitors as well as by hepatic clearance. Potential interaction of these two regulatory mechanisms was examined in the human hepatoma cell line Hep G2. These cells secrete plasminogen activator inhibitor type-1 (PAI-1) and initiate catabolism of exogenous t-PA by receptor-mediated endocytosis. Specific binding of 125I-t-PA to cells at 4 degrees C results in dose-dependent formation of a 95-kDa species recognized by monospecific anti-PAI-1 and anti-t-PA antibodies and stable in the presence of low (0.2%) concentrations of sodium dodecyl sulfate (SDS). Specific binding of 125I-t-PA and formation of the 95-kDa SDS-stable species are inhibited in a concentration-dependent manner following preincubation of cells with anti-PAI-1 antibodies. High and low molecular weight forms of urokinase plasminogen activator (u-PA) capable of forming specific complexes with PAI-1 complete for 125I-t-PA binding sites. However, the proenzyme form of u-PA (scu-PA), incapable of forming complexes with PAI-1, does not compete for 125I-t-PA binding sites. The role of the serine protease active site of t-PA in mediating both interaction with PAI-1 and specific binding was examined using 125I-t-PA that had been functionally inactivated with D-phenylalanyl-L-propyl-L-arginyl-chloromethyl ketone (PPACK). 125I-t-PA-PPACK, despite a 6-fold lower affinity than active 125I-t-PA, exhibited specific binding to cells without detectable formation of SDS-stable complexes with PAI-1. Both surface-bound 125I-t-PA and 125I-t-PA-PPACK are internalized and degraded by cells at 37 degrees C. 125I-t-PA is internalized as a stable complex with PAI-1, whereas 125I-t-PA-PPACK is internalized with similar kinetics but without the presence of an SDS-stable complex. Thus, PAI-1 appears capable of modulating t-PA catabolism in the human hepatocyte.
 ...
PMID:Catabolism of tissue-type plasminogen activator by the human hepatoma cell line Hep G2. Modulation by plasminogen activator inhibitor type 1. 254 Jan 81

Plasminogen activator inhibitor 1 (PAI-1) is the primary inhibitor of tissue-type plasminogen activator and thus performs an essential role in the regulation of the fibrinolytic process. It is a member of a large family of serine protease inhibitors (serpins). We determined the structure of the PAI-1 gene in order to more completely investigate the relationship of PAI-1 to other serpins and, at the same time, to begin to delineate structure-function relations in PAI-1 itself. A human genomic cosmid DNA library was screened and found to contain two independent clones, each harboring the entire PAI-1 gene. Restriction site mapping, electron microscopic inspection of heteroduplexes, and nucleotide sequence analysis all demonstrate that the PAI-1 gene is approximately 12.2 kilobase pairs in length and consists of nine exons and eight introns. All intron-exon boundaries are in accord with the "GT-AG" rule, including a cryptic acceptor splice site found in intron 7. The intron-exon pattern of the PAI-1 gene is distinct from that of most other serpins except that intron 3 of PAI-1 occupies an identical position as intron E of ovalbumin. Comparison of our data with the proposed subdomain structure of serpins suggests that seven of the eight introns may occupy a nonrandom position in the gene. These introns either delineate boundaries of individual structural subdomains or are located in random coil regions of the protein. Transcription of the PAI-1 gene in cultured vascular endothelial cells results in two distinct mRNA species. Our data suggest that these two transcripts arise by alternative polyadenylation.
 ...
PMID:Structure of the human plasminogen activator inhibitor 1 gene: nonrandom distribution of introns. 282 Apr 74

A human genomic phage library was screened using a human factor XII cDNA as a hybridization probe. Two overlapping phage clones were isolated which contain the entire human factor XII gene. DNA sequence and restriction enzyme analysis of the clones indicate that the gene is approximately 12 kilobase pairs in size and is comprised of 13 introns and 14 exons. Exons 3-14 are contained in a genomic region of only 4.2 kilobase pairs with introns ranging in size from 80 to 554 base pairs. The coding sequence of factor XII consists of multiple putative domains that are homologous to putative domains found in fibronectin and tissue-type plasminogen activator. These regions were found as separate exons in the gene. The intron/exon gene organization is similar to the serine protease gene family of plasminogen activators and not to the clotting factor family. Analysis of the 5' end of the gene shows that it does not contain the typical TATA and CAAT sequences found in other genes. This is consistent with the finding that transcription of the gene is initiated at multiple sites.
 ...
PMID:Characterization of the human blood coagulation factor XII gene. Intron/exon gene organization and analysis of the 5'-flanking region. 288 62

Tissue-type plasminogen activator (t-PA) is a serine protease with a molecular weight of about 70,000. It activates plasminogen to plasmin by cleavage of the Arg 560-Val 561 peptide bond. Kinetic analysis showed that the activation obeys Michaelis-Menten kinetics and that the presence of fibrin strikingly enhances the activation rate. The directed action of plasmin towards fibrin in vivo can be explained by the low Michaelis constant in the presence of fibrin (0.16 microM) which allows efficient plasminogen activation on a fibrin clot, while its high value in the absence of fibrin (65 microM) prevents efficient activation in plasma. Plasmin formed on the fibrin surface is protected from rapid inactivation by alpha 2-antiplasmin. Studies on the thrombolytic properties of t-PA (purified from melanoma cell cultures or obtained by recombinant DNA technology) in various animal models and in selected patients revealed that t-PA is a specific thrombolytic agent which induces thrombolysis without causing extensive systemic activation of the fibrinolytic system.
 ...
PMID:Tissue-type plasminogen activator. 295 11

The mammalian serine protease zymogen, plasminogen, can be converted into the active enzyme plasmin by vertebrate plasminogen activators urokinase (uPA), tissue plasminogen activator (tPA), factor XII-dependent components, or by bacterial streptokinase. The biochemical properties of the major components of the system, plasminogen/plasmin, plasminogen activators, and inhibitors of the plasminogen activators, are reviewed. The plasmin system has been implicated in a variety of physiological and pathological processes such as fibrinolysis, tissue remodeling, cell migration, inflammation, and tumor invasion and metastasis. A defective plasminogen activator/inhibitor system also has been linked to some thromboembolic complications. Recent studies of the mechanism of fibrinolysis in human plasma suggest that tPA may be the primary initiator and that overall fibrinolytic activity is strongly regulated at the tPA level. A simple model for the initiation and regulation of plasma fibrinolysis based on these studies has been formulated. The plasminogen activators have been used for thrombolytic therapy. Three new thrombolytic agents--tPA, pro-uPA, and acylated streptokinase-plasminogen complex--have been found to possess better properties over their predecessors, urokinase and streptokinase. Further improvements of these molecules using genetic and protein engineering tactics are being pursued.
 ...
PMID:Plasminogen activation: biochemistry, physiology, and therapeutics. 297 9


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>