943 Results for: "AbFrontier"

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ubiquitously expressed proteins which catalyze the reduction of hydrogen peroxides and organic hydroperoxides by glutathione. There are several isoforms which differ in their primary structure and localization. The classical cytosolic/mitochondrial GPx1 (cGPx) is a selenium-dependent enzyme, first of the GPx family to be discovered. GPx2, also known as gastrointestinal GPx (GI-GPx), is an intracellular enzyme expressed only at the epithelium of the gastrointestinal tract (1). Extracellular plasma GPx (pGPx or GPx3) is mainly expressed by the kidney from where it is released into the blood circulation (2). Phospholipid hydroperoxide GPx4 (PH-GPx) expressed in most tissues, can reduce many hydroperoxides including hydroperoxides integrated in membranes, hydroperoxy lipids in low density lipoprotein or thymine (3). All mammalian GPx family members, except for the recently described Cys containing GPx3 and epididymis-specific secretory GPx (eGPx or GPx5) isoforms, possess selenocysteine at the active site (4-5).

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Enolase (2-phosphogly-cerate hydrolyase or phosphopyruvate hydrates) is a glycolytic enzyme that catalyzes the dehydration and conversion of 2-phosphoglycerate to phosphoenolpyruvate. It comprises three distinct subunits, alpha, beta and gamma. Non Neuronal Enolase(ENO1) is an isoform of mammalian enolase and is composed of 2 alpha subunits. The gene for ENO1 also encodes a shorter monomeric structural lens protein, tau-crystallin.
Multifunctional enzyme that, as well as its role in glycolysis, plays a part in various processes such as growth control, hypoxia tolerance and allergic responses. May also function in the intravascular and pericellular fibrinolytic system due to its ability to serve as a receptor and activator of plasminogen on the cell surface of several cell-types such as leukocytes and neurons. Stimulates immunoglobulin production.
Used as a diagnostic marker for many tumors and, in the heterodimeric form, alpha/gamma, as a marker for hypoxic brain injury after cardiac arrest. Also marker for endometriosis. Antibodies against alpha-enolase are present in sera from patients with cancer-associated retinopathy syndrome (CAR), a progressive blinding disease which occurs in the presence of systemic tumor growth, primarily small-cell carcinoma of the lung and other malignancies. Is identified as an autoantigen in Hashimoto encephalopathy (HE) a rare autoimmune disease associated with Hashimoto thyroiditis (HT). HT is a disorder in which destructive processes overcome the potential capacity of thyroid replacement leading to hypothyroidism

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p38 MAPK cascade regulates a variety of cellular responses to stress, inflammation and other signals. p38 MAPK is relatively inactive in the non-phosphorylated form and becomes rapidly activated by dual phosphorylation of a Thr-Gly-Tyr motifs. There are four isoforms of p38 MAPK, , ,  and , which differ in their tissue expression and affinity for upstream activators and downstream effectors.
When cells are exposed to tumor necrosis factor-, interleukin-1, heat shock, or other activating stimuli, activation of MAPK kinase-3 and –6 occurs by phosphorylation. Activated MAPK kinase-3/6 phosphorylate each residue of Thr180 and Tyr182 in p38 MAPK. Phospho-p38 MAPK activates ATF-2, CHOP-1, MEF-2 and other transcription factors through phosphorylation.

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IκBα is the major IκB protein member of IκB family that function to inhibit the NF-κB transcription factor. IκBs have an N-terminal regulatory domain, followed by six or more ankyrin repeats and a PEST domain near their C terminus. IκBα inhibits NF-κB by masking the nuclear localization signals (NLS) of NF-κB proteins and keeping them in an inactive state in the cytoplasm. In addition, IκBα blocks the ability of NF-κB transcription factors to bind to DNA, which is required for NF-κB's proper functioning.
Upon stimulation by the proinflammatory cytokine tumor necrosis factor (TNF), signaling pathways lead to activation of the subunit of the IκB kinase (IKK) complex, which then phosphorylates IκB proteins on two N-terminal serine residues. The IKK is an unusual kinase in that it contains two related kinases, IKKα and IKKβ, and a regulatory subunit, NEMO (NF-κB essential modifier). The primary role of NF-κB is to maintain normal cellular functions that range from cell-to-cell communication to cell motility, cell cycle progression, and cell lineage development.

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Mitogen-activated protein kinases (MAPKs) are activated by various extracellular signals, such as growth factors, stresses, and cytokines, and play crucial roles in the determination of cell fate through proliferation, differentiation, survival, and apoptosis.
Mnk1(MAP kinase-interacting serine/threonine-protein kinase 1) and Mnk2 are protein kinases that are directly phosphorylated and activated by extracellular signal-regulated kinase (ERK) or p38 mitogen-activated protein (MAP) kinases which phosphorylate at least two threonine residues (Thr197 and Thr202 of the mouse Mnk1) located in the activation loop. Mnks are implicated in the regulation of protein synthesis through their phosphorylation of eukaryotic translation initiation factor 4E (eIF4E), also known as cap-binding protein.
The initiation step of translation is rate-limiting and represents a major target for translational control. The formation of the cap-binding complex eIF4F, which is a multiprotein factor responsible for the recruitment of the 40S ribosomal subunit to the mRNA 5′ end, is a key regulatory step. Mnk1 is physically associated with eIF4F and directly phosphorylate eIF4E, a component of the eIF4F complex. eIF4E specifically binds the 5′ m7GpppN cap structure found in all eukaryotic mRNAs and plays a critical role in cap-dependent translation initiation as a central component of the eIF4F complex, which also contains eIF4A and eIF4G.

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Bcl-2 (B-cell lymphoma 2) family govern mitochondrial outer membrane permeabilization (MOMP) and can be either pro-apoptotic (Bax, BAD, Bak, Bid and Bok) or anti-apoptotic (Bcl-2, Bcl-xL, and Bcl-w). Mitochondrial membrane permeabilization and subsequent release of apoptotic factors are key mechanisms during this process.
The members of the Bcl-2 family share one or more of the four characteristic domains of homology entitled the Bcl-2 homology (BH) domains (named BH1, BH2, BH3 and BH4).
Bid consists of only one Bcl-2 homology domain, BH3. Bid cleavage to tBid (truncated Bid) activates apoptotic pathway at the mitochondrial level. Cleavage of cytosolic Bid and subsequent mitochondrial translocation have been detected in neuronal cell death related to acute or chronic neurodegeneration. Pharmacological inhibition of Bid can be a promising therapeutic strategy in neurological diseases where programmed cell death is prominent.
After Bid activation and mitochondrial translocation, the most prominent downstream mechanisms of Bid-dependent neuronal apoptosis involve disruption of mitochondrial membrane integrity and intracellular calcium homoeostasis and the release of pro-apoptotic mitochondrial factors such as cytochrome c.

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The Smad family of proteins are functioning in the transmission of extracellular signals in the TGF-β signaling pathway. Binding of a TGF-β superfamily ligands to extracellular receptors triggers phosphorylation of Smad2 at a Serine-Serine-Methionine-Serine (SSMS) motif at its C-terminus. Phosphorylated Smad2 is then able to form a complex with Smad4. These complexes accumulate in the cell nucleus, where they are directly participating in the regulation of gene expression.
In mammals, eight Smad proteins have been identified to date. The Smad family of proteins can be divided into three functional groups: the receptor-activated Smads (R-Smads), common mediator Smads (Co-Smads), and the inhibitory Smads (I-Smads). The R-Smads are directly phosphorylated by the activated type I receptors on their C-terminal Ser-Ser-X-Ser (SSXS) motif and include Smad1, Smad2, Smad3, Smad5, and Smad8. Smad2 and Smad3 are phosphorylated in response to TGF-β and activin, whereas Smad1, Smad5, and Smad8 are phosphorylated in response to BMP (Bone Morphogenetic Protein). This C-terminal phosphorylation allows R-Smad binding to Co-Smad, Smad4, and translocation to the nucleus where they regulate TGF-β target genes. Smad6 and Smad7 belong to the I-Smad which bind to the type I receptor or Smad4 and block their interaction with R-Smads.
The Smads share sequence similarities, most notably in the N-terminal and carboxy-terminal regions, referred to as the MH1 (Mad Homology 1) and MH2 domains respectively. Smad2 and Smad3 have 66% amino acid sequence identity between their MH1 domains and 96% amino acid sequence identity between their MH2 domains.

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The complement system is a part of the larger immune system and three biochemical pathways are present: the classical complement pathway, the alternative pathway, and the mannose-binding lectin pathway.
Human complement factor C6 is one of five components (C5b, C6, C7, C8, and C9) that interact to form the cytolytic membrane attack complex (MAC) which is the cytolytic end product of the complement cascade. MAC is typically formed on the surface of intruding pathogenic bacterial as a result of the activation of the complement system, and it is one of the ultimate weapons of the immune system.
The sixth component of complement, C6, is a 913 amino acid single polypeptide chain serum glycoprotein. Homology study suggests that C6 could contain two domains, an amino-terminal region that is related to complement C8 and C9, and a carboxyl-terminal region that has partial homology to the complement regulatory proteins factor H and factor I.
Genetic deficiencies of terminal complement components lead to markedly increased susceptibility to only one particular Gram-negative genus, the Neisseria. The susceptibility is attributable to the major role played by complement-mediated killing in host defense against the pathogen.

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Btk (Bruton's tyrosine kinase) is a member of the Tec family of protein tyrosine kinases (PTKs) and plays a modulatory role in many cellular processes, such as proliferation, development, differentiation, survival, and apoptosis. The Tec kinases are the second largest family of non-receptor tyrosine kinases and include Tec, Btk, Bmx, Itk, and TXK/Rlk. Mutations of Btk gene cause a primary immunodeficiency disease in humans, X-linked aγglobulinemia (XLA) which is characterized by a lack of circulating B lymphocytes and an absence of immunoglobulins as a result of defects in B cell maturation and function. Btk is found in all hematopoietic cells, with the exception of T lymphocytes and plasma cells. Btk contains amino-terminal PH (pleckstrin homology) domain which binds phosphatidylinositol (3,4,5)-trisphosphate (PIP3) helping membrane translocation upon PI3 kinase activation. The Tec kinases have similar structure of N-terminal PH domains followed by Tec homology (TH), Src homology 3 (SH3), Src homology 2 (SH2), and kinase domains. Autophosphorylation of Tyr223 in SH3 domain is necessary for full activation of Btk. Various binding proteins have been reported to interact with different domains of Btk.

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IκB kinase α (IKKα) is a component of a multiprotein kinase complex that regulates the activity of the transcription factor NF-κB. Activation of the IKK complex via upstream stimuli leads to phosphorylation and degradation of NF-κB bound IκB(Inhibitor of κB). Subsequently, free NF-κB dimers enter the nucleus and regulate the transcription of a variety of target genes involved in cell proliferation and differentiation, apoptosis, and inflammation, etc. The IKK complex consists of 2 highly homologous kinase subunits, IKKα and IKKβ, and a nonenzymatic regulatory component, IKKγ/NEMO. The relative contributions of IKKα and IKKβ to the signalling complex vary according to the requirements of the cell. IKKβ plays a predominant role in immune responses, while IKKα alone appears to be sufficient for at least some developmental systems. Recently, IKK/NF-κB signaling pathway was studied as therapeutic targets in cancer.

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The Smad family of proteins are functioning in the transmission of extracellular signals in the TGF-β signaling pathway. Binding of a TGF-β superfamily ligands to extracellular receptors triggers phosphorylation of Smad2 at a Serine-Serine-Methionine-Serine (SSMS) motif at its C-terminus. Phosphorylated Smad2 is then able to form a complex with Smad4. These complexes accumulate in the cell nucleus, where they are directly participating in the regulation of gene expression.
In mammals, eight Smad proteins have been identified to date. The Smad family of proteins can be divided into three functional groups: the receptor-activated Smads (R-Smads), common mediator Smads (Co-Smads), and the inhibitory Smads (I-Smads). The R-Smads are directly phosphorylated by the activated type I receptors on their C-terminal Ser-Ser-X-Ser (SSXS) motif and include Smad1, Smad2, Smad3, Smad5, and Smad8. Smad2 and Smad3 are phosphorylated in response to TGF-β and activin, whereas Smad1, Smad5, and Smad8 are phosphorylated in response to BMP (Bone Morphogenetic Protein). This C-terminal phosphorylation allows R-Smad binding to Co-Smad, Smad4, and translocation to the nucleus where they regulate TGF-β target genes. Smad6 and Smad7 belong to the I-Smad which bind to the type I receptor or Smad4 and block their interaction with R-Smads.

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Glycogen synthase kinase-3β (GSK-3β) is a cytoplasmic serine/threonine protein kinase, which was initially identified as the kinase that phosphorylates glycogen synthase to inhibit glycogen synthesis. GSK3 β
is a ubiquitously expressed kinase that regulates a wide variety of cellular functions including metabolism, gene expression and cytoskeletal integrity. Akt/PI3K reduces GSK-3β activity by phosphorylation of its Ser9
residue. GSK-3 β has a critical role in the regulation of the amount of cyclin D1, as this kinase is involved in both cyclin D1 mRNA transcription and ubiquitin-dependent proteolysis.

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ERK1 and ERK2 are widely expressed and are involved in the regulation of meiosis, mitosis, and postmitotic functions in differentiated cells. Many different stimuli, including growth factors, cytokines, virus infection, ligands for heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptors and transforming agents, activate the ERK1 and ERK2 pathways.
When growth factors bind to the receptor tyrosine kinase, Ras interacts with Raf, the serine/threonine protein kinase and activates it as well. Once actived, Raf phosphorylates serine residue in 2 further kinases, MEK1/2, which in turn phosphorylates tyrosine/threonine in extracellular-signal regulated kinase(ERK) 1/2. Upon activation, the ERKs either phosphorylate a number of cytoplasmic targets or migrate to the nucleus, where they phosphorylate and activate a number of transcription factors such as c-Fos and Elk-1.

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The members of the Src-family kinases are Src, Lyn, Fyn, Yes, Hck, Lck, Fgr, Blk, and Yrk. Each of these have a common structure consisting of an unique domain at the N-terminal, followed by SH3, SH2 and tyrosine kinase domains.
In immume cells, the Src-family kinases play roles as critical regulators of a large number of intracellular signaling pathways, including integrin signaling pathway. Integrins are major cellular receptor that mediate cell to cell and cell to substratum interactions.
Src is expressed ubiquitously, however the expression level is higher in brain, osteoclasts, and platelets. Src plays a role in cell adhesion, cell morphology and motility, and bone resorption.
Src contains a 14-carbon myristoyl group attached to an SH4 domain, a unique domain, an SH3 domain, an SH2 domain, an SH2-kinase linker, a protein–tyrosine kinase domain (the SH1 domain), and a C-terminal regulatory segment.
One of the two most important regulatory phosphorylation sites in Src is Tyr527. Under basal conditions in vivo, 90–95% of Src is phosphorylated at Tyr527, and phosphotyrosine 527 binds intramolecularly with the Src SH2 domain. Tyrosine 416 is present in the activation loop and its phosphorylation promotes kinase activity.

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Transglutaminase(TGase) catalyses the crosslink of proteins by forming -(-glutamyl) lysine isopeptide bonds and requires the binding of Ca2+ for its activity. In mammals, eight distinct TGase isoenzymes have been identified. Tissue transglutaminase (tTGase), also known as TGase 2, has four distinct domains: N-terminal -sandwich, catalytic core and two C-terminal -barrel domains. tTGase may have a role in cell death, cell proliferation, cell differentiation, and receptor-mediated endocytosis. In the Alzheimer’s disease brain, the elevated tTGase activity is manifested by polymerization of a number of proteins, including A peptide, -amyloid precursor protein and the tau protein, with formation of neurofibrillary tangles.

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Lactoferrin(Lf), one of transferrin family, is found in external fluids, including milk and mucosal secretions, and prominent components of the secondary granules of neutrophils. Lf consists of a single polypeptide chain (approximately 80 kDa) folded into two structurally homologous lobes, each of which can reversibly bind one ferric ion (Fe3+). Lf plays a central role in iron metabolism and host defense system against microbial infection.

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Glutathione reductase (GR) is a member of pyridine nucleotide-disulfide oxidoreductases, which includes the closely related enzymes thioredoxin reductase, lipoamide dehydrogenase, trypanothione reductase and mercuric ion reductase. GR is a cytoplasmic flavoenzyme widely distributed in aerobic organisms. The dimeric protein is composed of two identical subunits, each containing 1 FAD and 1 redox-active disulfide/dithiol as components of the catalytic apparatus. It plays a role in maintaining glutathione (GSH) in its reduced form by catalyzing the reduction of glutathione disulfide (GSSG) (1):
GSSG + NADPH + H+  2GSH + NADP+
In most eukaryotic cells, GR maintains the ratio of [GSH]/[GSSG] elevated, and participates in several vital functions such as the detoxification of reactive oxygen species as well as protein and DNA biosynthesis (2).

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Peroxiredoxin (Prx) is a growing peroxidase family, whose mammalian members have been known to connect with cell proliferation, differentiation, and apoptosis.
Many isoforms (about 50 proteins), collected in accordance to the amino acid sequence homology, particularly amino-terminal region containing active site cysteine residue, and the thiol-specific antioxidant activity, distribute throughout all the kingdoms. Among them, mammalian Prx consists of 6 different members grouped into typical 2-Cys, atypical 2-Cys Prx, and 1-Cys Prx. Except Prx VI belonging to 1-Cys Prx subgroup, the other five 2-Cys Prx isotypes have the thioredoxin-dependent peroxidase (TPx) activity utilizing thioredoxin, thioredoxin reductase, and NADPH as a reducing system. Mammalian Prxs are 20 – 30 kilodalton in molecular size and vary in subcellular localization: Prx I, II, and VI in cytosol, Prx III in mitochondria, Prx IV in ER and secretion, Prx V showing complicated distribution including peroxisome, mitochondria and cytosol (1).

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Cyclin-dependent kinases (cdk) belong to a group of protein kinases originally discovered as being involved in the regulation of the cell cycle. Cdks are also involved in the regulation of transcription and mRNA processing. A Cdk is activated by association with a cyclin, forming a cyclin-dependent kinase complex.
Cdk1, also known as cell division control protein 2 (cdc2), is one of the components of the maturation promoting factor (MPF) which is essential for G1/S and G2/M phase transitions of eukaryotic cell cycle. Cdk1, when bound to cyclin B, allows a dividing cell to enter into mitosis from G2 and permits the transition from G1 through S in conjunction with cyclin A and cyclin E. The Cdk1 protein is constantly present throughout the cell division cycle, but its activity is finely tuned by means of protein-protein interactions and reversible phosphorylation.
Cdk1 can also enhance cell migration. Increased levels of Cdk1 promote cell migration together with cyclin B2 and the actin-stabilizing protein caldesmon. Phosphorylation of caldesmon bound to actin results in the displacement of caldesmon from actin followed by the altered interaction of actin with myosin. These events contribute to increased cell migration.

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Noggin is a 32 kDa glycoprotein that binds to bone morphogenetic protein (BMP) and antagonizes the action of them. Bone morphogenetic proteins were originally identified by an ability of demineralized bone extract to induce endochondral osteogenesis in vivo. BMPs also regulate cell proliferation, differentiation, lineage determination, motility, and death. BMP antagonists include noggin, chordin, follistatin, ventroptin, twisted gastrulation, Dan, and gremlin etc. They play a crucial role in bone development, by regulating the BMP functions.
Noggin plays a key role in neurulation by inhibiting BMP4, along with other morphogens such as chordin and follistatin and in the formation of the neural plate. Noggin inhibits BMP signaling by blocking the molecular interfaces of the binding epitopes for both type I and type II receptors. It antagonizes the action of BMPs, and induces neural tissue and dorsalizes ventral mesoderm.

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p38 MAPK cascade regulates a variety of cellular responses to stress, inflammation and other signals. p38 MAPK is relatively inactive in the non-phosphorylated form and becomes rapidly activated by dual phosphorylation of a Thr-Gly-Tyr motifs. There are four isoforms of p38 MAPK, , ,  and , which differ in their tissue expression and affinity for upstream activators and downstream effectors.
When cells are exposed to tumor necrosis factor-, interleukin-1, heat shock, or other activating stimuli, activation of MAPK kinase-3 and –6 occurs by phosphorylation. Activated MAPK kinase-3/6 phosphorylate each residue of Thr180 and Tyr182 in p38 MAPK. Phospho-p38 MAPK activates ATF-2, CHOP-1, MEF-2 and other transcription factors through phosphorylation.

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Fibronectin is a high molecular weight glycoprotein containing about 5% carbohydrate that binds to receptor proteins that span the cells membrane, called integrins. In addition to integrins, they also bind extracellular matrix components such as collagen, fibrin and heparin. Fibronectin can be found in the blood plasma in its soluble form which is composed of two 250 kDa subunits joined together by disulfide bonds. Plasma fibronectin is made in the liver by hepatocytes. The insoluble form that serves as a linker in the extracellular matrix is a large complex of cross-linked subunits. Fibronectin is involved in many cellular processes, including tissue repair, embryogenesis, blood clotting, and cell migration/ adhesion, so it can be used as a therapeutic agent for wound healing. It is also one of the few proteins for which production increases with age without any associated pathology.

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PRAK is a 471 amino acid protein with 20-30% sequence identity to the known MAP kinase-regulated protein kinases RSK1/2/3, MNK1/2 and MAPKAPK2/3.
The p38 mitogen-activated protein kinase (MAPK) pathway plays an important role in cellular responses to inflammatory stimuli and environmental stress. There are at least six protein kinases that can be regulated by p38α and/or p38β. These downstream kinases of p38s include MAPK-activated protein kinase 2 (MAPKAPK2 or MK2), MAPKAPK3, MAPK-interacting kinase 1 (MNK1), MNK2, p38-activated/regulated protein kinase (PRAK or MAPKAPK5), and mitogen- and stress-activated protein kinase (MSK). PRAK can be activated in response to cellular stress and proinflammatory cytokines. T182 within the activation loop of PRAK has been determined to be the regulatory phosphorylation site. PRAK has been reoprted to be essential for ras-induced senescence and tumor suppression. PRAK mediates senescence upon activation by p38 in response to oncogenic ras.

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Prothrombin precursor is synthesized in liver as a precursor of prothrombin containing a signal sequence and a propeptide domain at the N-terminus. Before its secretion into plasma, this precursor undergoes several posttranslational modifications, including removal of signal sequence and propeptide domains, glycosylation, and γ-glutamyl-carboxylation reaction. Prothrombin, cleaved by the prothrombinase enzyme complex that consists of serine protease factor Xa, cofactor Va, phospholipids and calcium, is converted to thrombin which converts fibrinogen into fibrin which in turn strengthens a protective clot. Activation of prothrombin is crucial in physiological and pathological coagulation. Various rare diseases involving prothrombin(e.g. hypoprothrombinemia) have been described.

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Myeloperoxidase is a major neutrophil protein and is also present in monocytes. In neutrophils, it is stored in azurophilic granules and released during phagocytosis. It is a heme enzyme that uses the superoxide and hydrogen peroxide generated by the neutrophil oxidative burst to produce hypochlorous acid and other reactive oxidants.The produced hypochlorous acid reacts with and destroys bacteria. In many inflammatory pathologies, such as cystic fibrosis and rheumatoid arthritis, neutrophils are also causing tissue damage. MPO is thought to be the most promising cardiac marker at the moment. In addition to that MPO is a good inflammatory biomarker for autoimmune, inflammatory diseases and cancer.

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Dual specificity phosphatase(DUSP) inactivate their target kinases by dephosphorylating both the phosphoserine/threonine and phosphotyrosine residues. DUSPs can be divided into six subgroups on the basis of sequence similarity(PRLs, Cdc14 phosphatases, PTENs, myotubularins, MKPs, atypical DUSPs). DUSP inhibitors might be used to manipulate MAPK and cellular responses in both positive and negative ways. The regulated expression and activity of DUSP family members in different cells and tissues controls MAPK intensity and duration to determine the type of physiological response.
DUSP12(YVH1, GKAP) contains the consensus DUSP catalytic domain as well as an extended C-terminal domain of unknown function, thought to be related to its potential role in glucokinase regulation. It is localized in the cytoplasm and nucleus.

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The complement system is a part of the larger immune system and three biochemical pathways are present: the classical complement pathway, the alternative pathway, and the mannose-binding lectin pathway.
The biological functions of complement are opsonization and phagocytosis, stimulation of inflammatory reactions and lysis of bacteria.
C1 complex (C1q, C1r and C1s) is the first component of the classical pathway of complement activation which occurs when C1q binds to IgM or IgG complexed with antigens, or when C1q binds directly to the surface of the pathogen. Binding of C1 to immunoglobulins in the form of immune complexes leads to activation of proteases C1r and C1s, and the cleavage of C2 and C4 producing C2a and C4b. C4b and C2a bind to form C3-convertase.
C1q is a hexamer composed of globular heads attached to collagen-like triple-helix tails. The globular heads of C1q specifically bind to the CH2 domain of IgG molecules or the CH3 domain of IgM.
In mammals, hepatocyte is the major source of most C proteins with the exception of C1q, factor D and C7. Interestingly, C1q mRNA is essentially
expressed in spleen, thymus and heart.
C1q knockout mice show a profound impairment in the clearance of apoptotic cells which then accumulate in the kidney leading to glomerulonephritis with immune deposits. Individuals with deficiency of C1q have the highest prevalence of systemic lupus erythematosus.

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Peroxiredoxin (Prx) is a growing peroxidase family, whose mammalian members have been known to connect with cell proliferation, differentiation, and apoptosis.
Many isoforms (about 50 proteins), collected in accordance to the amino acid sequence homology, particularly amino-terminal region containing active site cysteine residue, and the thiol-specific antioxidant activity, distribute throughout all the kingdoms. Among them, mammalian Prx consists of 6 different members grouped into typical 2-Cys, atypical 2-Cys Prx, and 1-Cys Prx. Except Prx VI belonging to 1-Cys Prx subgroup, the other five 2-Cys Prx isotypes have the thioredoxin-dependent peroxidase (TPx) activity utilizing thioredoxin, thioredoxin reductase, and NADPH as a reducing system. Mammalian Prxs are 20 – 30 kilodalton in molecular size and vary in subcellular localization: Prx I, II, and VI in cytosol, Prx III in mitochondria, Prx IV in ER and secretion, Prx V showing complicated distribution including peroxisome, mitochondria and cytosol.

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Peroxiredoxin (Prx) is a growing peroxidase family, whose mammalian members have been known to connect with cell proliferation, differentiation, and apoptosis.
Many isoforms (about 50 proteins), collected in accordance to the amino acid sequence homology, particularly amino-terminal region containing active site cysteine residue, and the thiol-specific antioxidant activity, distribute throughout all the kingdoms. Among them, mammalian Prx consists of 6 different members grouped into typical 2-Cys, atypical 2-Cys Prx, and 1-Cys Prx. Except Prx VI belonging to 1-Cys Prx subgroup, the other five 2-Cys Prx isotypes have the thioredoxin-dependent peroxidase (TPx) activity utilizing thioredoxin, thioredoxin reductase, and NADPH as a reducing system. Mammalian Prxs are 20 – 30 kilodalton in molecular size and vary in subcellular localization: Prx I, II, and VI in cytosol, Prx III in mitochondria, Prx IV in ER and secretion, Prx V showing complicated distribution including peroxisome, mitochondria and cytosol (1).

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Vimentin is a member of the intermediate filament family of proteins found in various non-epithelial cells, especially mesenchymal cells. Vimentin is responsible for maintaining cell shape, integrity of the cytoplasm, and stabilizing cytoskeletal interactions. Vimentin plays a significant role in supporting and anchoring the position of the organelles in the cytosol. Although most intermediate filaments are stable structures, vimentin also has a dynamic nature which is important when offering flexibility to the cell.
Two monomers which have central α-helical domains, capped on each end by non-helical domains twist around each other to form a coiled-coil dimer. Two dimers then form a tetramer, which, in turn, form a sheet by interacting with other tetramers.
There are some reports related to the biochemical function of intermediate filament network. The intracellular movement of LDL-derived cholesterol from the lysosome to the site of esterification is a vimentin-dependent process. A role for vimentin in mechanotransduction of shear stress has also been suggested. The mechanical stress of fluid shear on endothelial cells seems to trigger MAPK signaling pathways and stimulates proliferation.