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Reversible phosphorylation of tyrosine residues is a key regulatory mechanism for numerous cellular events such as proliferation, differentiation, gene expression and migration. Abnormalities in tyrosine phosphorylation play a role in the pathogenesis of numerous inherited or acquired human diseases from cancer to immune deficiencies.
There are at least 107 genes coding for PTPs (protein tyrosine phosphatases) in the human genome.
All known PTPs contain a highly conserved 12 amino acid catalytic
domain and are further distinguished on the basis of additional structural motifs. The receptor-like PTPs exhibit an extracellular domain, a single transmembrane and one or two intracellular phosphatase domains. The nonreceptor cytoplasmic PTPs contain a single phosphatase domain and additional amino acid sequences that are homologous to motifs found in other classes of proteins.
Protein tyrosine phosphatases PTPN5 (STEP), PTPRR and PTPN7 comprise a family of phosphatases that specifically inactivate MAPKs (mitogen-activated protein kinases).
There are multiple forms of STEP in the adult rat brain which show differential enrichment in brain regions implicated in aspects of cognitive,
affective, and motor behaviors. Some of the STEP isoforms are generated through alternative splicing of a single STEP gene and each has unique intracellular targets and functions.

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Anti-mRNA capping enzyme Mouse Monoclonal Antibody [clone: T16-AF3F1]

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Superoxide dismutase (SOD) is an antioxidant enzyme involved in the defense system against reactive oxygen species (ROS). SOD catalyzes the dismutation reaction of superoxide radical anion (O2-) to hydrogen peroxide, which is then catalyzed to innocuous O2 and H2O by glutathione peroxidase and catalase. Several classes of SOD have been identified. These include intracellular copper, zinc SOD (Cu, Zn-SOD/SOD-1), mitochondrial manganese SOD (Mn-SOD/SOD-2) and extracellular Cu, Zn-SOD (EC-SOD/SOD-3) (1). SOD-1 is found in all eukaryotic species as a homodimeric 32 kDa enzyme containing one each of Cu and Zn ion per subunit (2). The manganese containing 80 kDa tetrameric enzyme SOD2, is located in the mitochondrial matrix in close proximity to a primary endogenous source of superoxide, the mitochondrial respiratory chain (3). SOD-3 is a heparin-binding multimer of disulfide-linked dimers, primarily expressed in human lungs, vessel walls and airways (4). SOD-4 is a copper chaperone for superoxide dismutase (CCS), which specifically delivers Cu to copper/zinc superoxide dismutase. CCS may activate copper/zinc superoxide dismutase through direct insertion of the Cu cofactor.

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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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Signal transducer and activator of transcription (STAT), named after their dual role, generally mediate cytokine, growth factor and hormone receptor signal transduction. In mammals, seven STAT proteins have been identified. STAT5 has been implicated in cellular functions of proliferation, differentiation and apoptosis with relevance to processes of hematopoiesis and immunoregulation, reproduction, and lipid metabolism. Two highly homologous STAT5 isoforms, 96kDa STAT5a and 94kDa STAT5b, are encoded by two tandemly linked genes. Although both STAT5 isoforms are roughly 95% homologous at the level of cDNA, they exhibit both redundant and non-redundant functions in vivo, probably due to differences in their transactivation domain. Aberrant regulation of STAT5 has been observed in solid tumors as well as in patients with either chronic or acute myeloid leukemia. Kinase inhibitors are currently being developed to negatively regulate STAT5 activity for clinical purposes.

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Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a catalytic enzyme commonly known to be involved in glycolysis. The enzyme exists as a tetramer of identical 37 kDa subunits. GAPDH catalyzes the reversible reduction of 1,3-bisphos-phoglycerate to glyceraldehyde 3-phosphophate in the presence of NADPH. Apart from playing a key role in glycolysis, this ubiquitously expressed enzyme also displays other activities unrelated to its glycolytic function. GAPDH is reported to be involved in the processes of DNA replication (1), DNA repair (2), nuclear RNA export (3-4), membrane fusion (5) and microtubule bundling. Other studies also provide evidence of GAPDH playing an essential part of the program of gene expression observed in apoptosis and as part of the cellular phenotype of age-related neurodegenerative diseases (6-7).

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There are ten mitogen-activated protein kinase (MAPK) phosphatases (MKPs) that act as negative regulators of MAPK activity in mammalian cells.
MKP2(DUSP4) is a dual threonine/tyrosine phosphatase that specifically dephosphorylates and inactivates MAPKs(ERK, JNK, p38). It contains one Rhodanese domain and one tyrosine-protein phosphatase domain.
MKP2 is expressed in a variety of tissues, and is localized in the nucleus.
Transcription factor E2F-1 acts as a transcriptional regulator of MKP2. E2F-1/MKP2 pathway mediates apoptosis under oxidative stress and that MKP2 suppresses tumor formation.
MKP2 is a novel transcription target of p53 in mediating apoptosis by 10-bp palindrome motif (CTGGCGCCAG) in the MKP2 promoter.

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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.

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Plasmid vectors for the expression of coding regions of eukaryotic genes in bacterial, insect and mammalian hosts are in common usage. The expression vectors are used to encode hybrid fusion proteins consisting of a eukaryotic target protein and a specialized region designed to aid in the
purification and visualization of the target protein. Short pieces of welldefined peptides(Poly-His, Flag-epitope or cmyc epitope or HA-tag) or small proteins (bacterial GST, MBP) is often cloned along with the target gene. The HA tag is derived from an epitope of the influenza hemagglutinin protein, which has been extensively used as a general epitope tag in expression vectors. It has been successfully used in a
variety of applications, including Western blotting, Immunoprecipitation, and immunofluorescence studies.

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Synuclein is a small, soluble protein primarily expressed in neural tissue. The synuclein family includes three known proteins: α-synuclein, β-synuclein, and γ-synuclein.
α-Synuclein is a very conserved, small acidic protein (140 residues) with a molecular weight of approximately 19 kDa that accounts for about 1% of total protein in neurons. It is concentrated primarily in presynaptic axon terminals and plays a central role in initiating Parkinson’s disease. It is the principal constituent of Lewy bodies which are formed by protein aggregation and inclusion body formation.
α-Synuclein lacks secondary or tertiary structure, so it belongs to the family of natively unfolded proteins, many of which act as chaperones. Much of this α-synuclein has been post-translationally modified to increase the rate of oligomerization.
Mutant forms of α-Synuclein are associated with autosomal dominant Parkinson’s disease. The mutations increase the aggregation rate of the resultant α-synuclein
β-Synuclein is found primarily in brain tissue and is seen mainly in presynaptic terminals. It is predominantly expressed in the neocortex, hippocampus, striatum, thalamus, and cerebellum.
β-Synuclein may protect the central nervous system from the neurotoxic effects of α-synuclein by inhibiting aggregation of α-synuclein which occurs in neurodegenerative diseases such as Parkinson's disease.
γ-Synuclein is a synuclein protein found primarily in the peripheral nervous system (in primary sensory neurons, sympathetic neurons, and motor neurons) and retina. γ-Synuclein expression in breast tumors is a marker for tumor progression.

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Cyclin-dependent kinase-5(CDK5) is a member of the cyclin-dependent kinase family of serine/threonine kinases. Its mRNA and protein are expressed in the kidneys, testes, and ovaries. And Its activity has been detected almost exclusively in brain extracts. Similar to other Cdks, monomeric Cdk5 displays no enzymatic activity; however, Cdk5 is not activated by cyclins. Instead, Cdk5 activity requires association with one of two brain-specific regulatory subunits, called p35 and p39. These two activators regulate the spatial and temporal expression of active Cdk5, restricting its activity primarily to post-mitotic neurons.

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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 nucleotidebinding 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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Anti-Peroxiredoxin 5 Rabbit Polyclonal Antibody

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PTEN acts as a phosphatase to dephosphorylate phosphatidylinositol (3,4,5)-trisphosphate (PtdIns (3,4,5)P3). The product of this enzymatic reaction is PtdIns(4,5)P2. This dephosphorylation is important because it results in inhibition of the AKT signaling pathway.
PTEN is a 403 amino acid protein, and a member of the large PTP (protein tyrosine phosphatase) family. PTEN crystal structure revealed that the N-terminal phosphatase domain is followed by a tightly associated C-terminal C2 domain. These two domains together form a minimal catalytic unit. The phosphatase domain contains the active site which carries out the enzymatic function of the protein, whilst the C2 domain allows PTEN to bind to the phospholipid membrane.
PTEN is one of the most commonly lost tumour suppressors in human cancer, and its deregulation is also implicated in several other diseases. Hereditary mutation of PTEN causes tumor-susceptibility diseases such as Cowden disease.

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Mammalian target of rapamycin (mTOR), a serine/threonine kinase involved in diverse cellular processes, including protein translation, mRNA turnover, and protein stability, mediates, at least in part, some of the biological actions of Akt. As a Kinase subunit of both mTORC1(complex1) and mTORC2(complex2), mTOR regulates cell growth and survival in response to nutrient and hormonal signals. mTORC1 is activated in response to growth factors or amino-acids. Activated mTORC1 up-regulates protein synthesis by phosphorylating key regulators of mRNA translation and ribosome synthesis. mTORC1 phosphorylates EIF4EBP1 and releases it from inhibiting the elongation initiation factor 4E (eiF4E). mTORC2 seems to function upstream of Rho GTPases to regulate the actin cytoskeleton, probably by activating one or more Rho-type guanine nucleotide exchange factors. mTORC2 promotes the serum-induced formation of stress-fibers or F-actin. mTORC2 plays a critical role in AKT1 'Ser-473' phosphorylation.

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Anti-PTPRM Mouse Monoclonal Antibody [clone: T5-AF1A8]

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Dual specificity phosphatase 13(Also known as BEDP; MDSP; TMDP; SKRP4; DUSP13A; DUSP13B) is an enzyme that in humans is encoded by the DUSP13 gene.[1]
Members of the protein tyrosine phosphatase superfamily cooperate with protein kinases to regulate cell proliferation and differentiation. This superfamily is separated into two families based on the substrate that is dephosphorylated. One family, the dual specificity phosphatases (DSPs) acts on both phosphotyrosine and phosphoserine/threonine residues. This gene encodes different but related DSP proteins through the use of non-overlapping open reading frames, alternate splicing, and presumed different transcription promoters. Expression of the distinct proteins from this gene has been found to be tissue specific and the proteins may be involved in postnatal development of specific tissues. A protein encoded by the upstream ORF was found in skeletal muscle, whereas the encoded protein from the downstream ORF was found only in testis. In mouse, a similar pattern of expression was found. Multiple alternatively spliced transcript variants were described, but the full-length sequence of only some were determined.[1]

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The RIP(receptor-interacting protein) family of serine/Threonine kinases(RIP-1,2,3,4,5,6,7) are crucial regulators of cell survival and cell death that can trigger pro-survival, inflammatory and immune responses via the activation of transcription factors(NF-kB and AP-1) and death-inducing programs.
RIP2(also known as RICK, CARDIAK, CCK and Ripk2) transduces signals from receptors of both immune responses. RIP2 carries a CARD at its C-terminal, which is essential for NF-kB activation. RIP2 is a critical downstream mediator of Nod1 and Nod2 signaling. Overexpression of RIP2 results in the activation of, in addition to NF-kB, the MAPKs JNK and ERK2, requiring its kinase activity to activate ERK2, but not JNK.

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Focal adhesion kinase subfamily consists of the non-receptor proline-rich protein tyrosine kinases (PTKs). Two members of the family are focal adhesion kinase (FAK) and proline-rich tyrosine kinase 2 (PYK2). These two kinases have molecular mass between 110-125 kDa and are closely related in their structure. The presence of two proline-rich motifs within the C-terminal domains is conserved.
FAK is a nonreceptor and nonmembrane associated PTK which does not contain Src homology 2 (SH2) or SH3 protein interaction domains. The centrally located kinase domain of FAK is flanked by large N- and C-terminal noncatalytic domains.
FAK links integrin receptors to intracellular signaling pathways that are important for cell growth, survival, and migration. Integrin receptor engagement with ligands such as fibronectin can stimulate FAK autophosphorylation which enables FAK to function within a network of integrin-stimulated signaling pathways leading to the activation of targets such as the ERK and JNK/mitogen-activated protein kinase pathways. Recent study reveals that FAK is essential for angiogenesis in the embryo, functions in heart development and modulates the response of cardiomyocytes to pressure overload in adult mice.

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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.

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Heat shock proteins are ubiquitous proteins and have been characterized as cytoprotective molecular chaperones. The typical function of a chaperone is to assist a protein to attain its functional conformation to prevent non-functional aggregation of misfolded proteins. The principal HSP families are HSP90, HSP70, HSP60 and the small HSPs including HSP27, ubiquitin, α-crystallin, Hsp20 and others. The common functions of small Hsps are chaperone activity, thermotolerance, inhibition of apoptosis, regulation of cell development, and cell differentiation.
Hsp27 has a molecular weight of approximately 27 kDa, although it has been shown to form large aggregates of up to 800 kDa in the cytosol. Hsp27 is found in several types of human cells, including tumour cells. Hsp27 interferes with apoptosis through its ability to interact with and inhibit key components of the apoptotic signaling pathway, including the caspase activation complex. Overexpression of heat shock proteins can increase the tumorigenic potential of tumour cells. HSP27 also has been reported to be involved in development and progression of hormone-refractory prostate cancer.

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Amphiphysins, members of the BAR (Bin-Amphiphysin-Rvsp) protein super family, play a key role in clathrin-mediated endocytosis of synaptic vesicles (SVs). All members of the BAR family share a highly conserved N-terminal BAR domain and a C-terminal Src homology (SH3) domain. Two isoforms of amphiphysin have been identified and act in concert as a heterodimer. Amphiphysins interact via its carboxy-terminal SH3 domain with dynamin, synaptojanin and clathrin. These complexes are implicated in synaptic vesicle recycling at nerve terminal.  Amphiphysins were also identified as the dominant autoantigen in paraneoplastic Stiff-Man Syndrome.

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Ataxia telangiectasia mutated (ATM) is a serine/threonine-specific protein kinase that is activated by DNA double-strand breaks. It phosphorylates several key proteins that initiate activation of the DNA damage checkpoint, leading to cell cycle arrest, DNA repair or apoptosis. Several of these targets are p53, CHK2, BRCA1, and H2AX.
ATM triggers the G1/S checkpoint; ATR (Ataxia telangiectasia and Rad3-related) prevents G1/S stasis. In this single point in the cell cycle, it would appear that ATM and ATR function in opposition to one another.
Ataxia telangiectasia (AT) is a rare neurodegenerative, autosomal recessive disorder characterized by chromosome instability, radiosensitivity, immunodeficiency and a predisposition for cancer.
The ATR (ATM and Rad3-related) kinase and its downstream effector kinase, Chk1, are central regulators of the replication checkpoint. Loss of these checkpoint proteins causes replication fork collapse and chromosomal rearrangements. ATR are thought to be master controllers of cell cycle checkpoint signaling pathways that are required for cell response to DNA damage and for genome stability.

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α-fetoprotein (AFP) is a glycoprotein of 590 amino acids containing 3.4% carbohydrate content with a molecular weight of 61,000 – 75,000 Da. AFP is normally produced in the developing embryo and fetus by the fetal yolk sac, the fetal gastrointestinal tract, and eventually by the fetal liver. In humans, AFP levels decrease gradually after birth, reaching adult levels by 8 to 12 months. Normal adult AFP levels are low and AFP has no known function in normal adults.
The biologic role of AFP has not been defined yet. Because of its biochemical similarity to albumin, it has been postulated that AFP could be a carrier protein. It may have an immunoregulatory function during pregnancy.
Increased serum levels are found in some tumors, such as hepatocellular
carcinoma (HCC), hepatoblastoma, and germ cell tumors. Although total AFP is a useful serological marker for diagnosis of HCC, the false-negative or positive rate with AFP level is very high. AFP-L3, an isoform of AFP which binds Lens culinaris agglutinin, can be particularly useful in early identification of aggressive tumors associated with HCC. AFP mRNA, the circulating genetic markers, also has been used in monitoring distal metastasis or postoperative recurrence of HCC.

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Cyclin-dependent kinase-5(CDK5) is a member of the cyclin-dependent kinase family of serine/threonine kinases. Its mRNA and protein are expressed in the kidneys, testes, and ovaries. And Its activity has been detected almost exclusively in brain extracts.
Similar to other Cdks, monomeric Cdk5 displays no enzymatic activity; however, Cdk5 is not activated by cyclins. Instead, Cdk5 activity requires association with one of two brain-specific regulatory subunits, called p35 and p39. These two activators regulate the spatial and temporal expression of active Cdk5, restricting its activity primarily to post-mitotic neurons.

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The mammalian Phospholipase C(PLC) family has two closely related proteins, PLC1 and PLC2. The PLC isozymes have the core structure domains and a unique array of domains containing an additional PH domain, two SH2 domains and one SH3 domain. In response to extracellular stimuli, such as hormones and growth factors, receptor tyrosine kinases (RTKs) phosphorylate and activate PLC. Activated PLC catalyzes hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) to produce the metabolic second messenger molecules inositol 1,4,5-triphosphate (IP3) and diacylglycerol (DAG).

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STAT2 (Signal transducer and activator of transcription 2), 113kDa, is a member of the STAT family of cytoplasmic transcription factors. STAT members generally mediate cytokine, growth factor and hormone receptor signal transduction. STAT2 is a transcription factor critical to the signal transduction pathway of type I interferons (e.g. IFNα). STAT2 resides primarily in the cytoplasm and is tyrosine-phosphorylated after IFNα binds to cell surface receptors. In response to tyrosine phosphorylation STAT2 rapidly localizes to the nucleus and acquires the ability to bind specific DNA targets in association with two other proteins, STAT1 and IFN regulatory factor-9 (IRF-9). STAT2 is phosphorylated at Y689 by receptor-associated Janus kinasses (JAKs) leading to STAT2 dimerization and subsequent translocation to the nucleus to activate gene transcription.

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14-3-3, a family of acidic and soluble proteins, highly conserved in amino acid sequences from yeast to mammals, is expressed in all eukaryotic cells. Seven isoforms(β, γ, ε, η, ζ, σ and τ/θ) encoded by seven distinct genes are identified in mammals and forms homo- and hetero- dimeric cup-shaped structures. As 14-3-3 is interacted with more than 100 binding partners, it regulates key proteins involved in various biological processes such as signal trans-duction, cell cycle, transcriptional control, cell proliferation, apoptosis, and ion channel physiology. Most 14-3-3 requires phosphorylation of serine or threonine residues in the target sequence. This protein is abundantly expressed in the brain and has been detected in the cerebrospinal fluid of patients with different neurological disorders.

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Superoxide dismutase (SOD) is an antioxidant enzyme involved in the defense system against reactive oxygen species (ROS). SOD catalyzes the dismutation reaction of superoxide radical anion (O2-) to hydrogen peroxide, which is then catalyzed to innocuous O2 and H2O by glutathione peroxidase and catalase. Several classes of SOD have been identified. These include intracellular copper, zinc SOD (Cu, Zn-SOD/SOD-1), mitochondrial manganese SOD (Mn-SOD/SOD-2) and extracellular Cu, Zn-SOD (EC-SOD/SOD-3) (1). SOD1 is found in all eukaryotic species as a homodimeric 32 kDa enzyme containing one each of Cu and Zn ion per subunit (2). The manganese containing 80 kDa tetrameric enzyme SOD2, is located in the mitochondrial matrix in close proximity to a primary endogenous source of superoxide, the mitochondrial respiratory chain (3). SOD3 is a heparin-binding multimer of disulfide-linked dimers, primarily expressed in human lungs, vessel walls and airways (4). SOD4 is a copper chaperone for superoxide dismutase (CCS), which specifically delivers Cu to copper/zinc superoxide dismutase. CCS may activate copper/zinc superoxide dismutase through direct insertion of the Cu cofactor.

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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).