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Cathepsin-E also known as CTSE is a gastric aspartyl protease which functions as a disulfide-linked homodimer. CTSE belongs to the peptidase C1 family; furthermore it has specificity similar to pepsin A and cathepsin D. CTSE is an intracellular proteinase which does not seem to be involved in the digestion of dietary protein and is found in the uppermost concentration in the surface of epithelial mucus-producing cells of the stomach. CTSE is the first aspartic proteinaseexpressed in the fetal stomach and is discovered in more than half of gastric cancers. For that reason CTSE is anoncofetal antigen. In addition, transcript variants utilizing alternative polyadenylation signals and two transcript variantsencoding different isoforms exist for this gene.

DCUN1D1 takes part in the malignant transformation of squamous cell lineage. DCUN1D1 protein regulates Gli1, a main regulator of the hedgehog (HH) pathway which takes a vital role in development, maintenance, and regeneration of practically all adult tissues.

EFNB1 is a member of the Eph family. The cell-surface proteins Ephrins split into two groups, ephrin-A and ephrin-B, based on their structure and function and perform as ligands for Eph receptors. The transmembrane EFNB1 proteins have conserved cytoplasmic tyrosine residues that are phosphorylated upon interaction with an EphB receptor. In addition, EFNB1 transduces outside-in signals by C-terminal protein interfaces which influence integrin-mediated cell attachment and migration.

EMAP-II also called SCYE1 is a tumor derived cytokine that plays a role in a wide variety of activities on endothelial cells, monocytes and neutrophils. EMAP-II inhibits endothelial cell proliferation, vasculogenesis, neovessel formation, and can induce apoptosis. It is also chemotactic towards neutrophils and monocytes and induces myeloperoxidase activity from neutrophils. EMAP-II clinical value is inhibiting angiogenesis of vascular beds and suppressing the growth of primary and secondary tumors with no affect to normal tissues. SCYE1is specifically induced by apoptosis, and it is involved in the control of angiogenesis, inflammation, and wound healing. The release of this SCYE1 renders the tumor-associated vasculature sensitive to tumor necrosis factor. The precursor protein is identical to the p43 subunit, which is associated with the multi-tRNA synthetase complex, and it modulates aminoacylation activity of tRNA synthetase in normal cells. EMAP-2 plays a role in in the stimulation of inflammatory responses after proteolytic cleavage in tumor cells.

Sorcin (SRI) which is a 22kDa calcium-binding protein was originally identified in multidrug-resistant cells. Sorcin, which modulates excitation-contraction coupling in the heart, contributes to calcium homeostasis in the heart sarcoplasmic reticulum.

Procollagen C-endopeptidase enhancer 1, also known as PCOLCE binds to the C-terminal propeptide of type I procollagen and enhances procollagen C-proteinase activity. In addition, C-terminal processed part of PCPE (CT-PCPE) has a metalloproteinase inhibitory activity. Among the diseases which are associated with PCOLCE: bone fracture & oculopharyngeal muscular dystrophy.

C1QTNF3 also called Cartducin is a novel angiogenic factor in the formation of neointima following angioplasty. C1QTNF3 a paralog of Acrp30 (adiponectin). C1QTNF3 is a secretory protein produced by chondrogenic precursors & proliferating chondrocytes, and belongs to a novel C1q family of proteins. Cartducin promotes the growth of mesenchymal chondroprogenitor cells & chondrosarcoma-derived chondrocytic cells in vitro. Cartducin stimulates mesenchymal chondroprogenitor cell proliferation through extracellular signal-regulated kinase and phosphatidylinositol 3-kinase/Akt pathways. C1QTNF3 promotes proliferation & the migration of endothelial cells.

Calmodulin Like 5, also known as CALML5 is a part of the calmodulin family of calcium binding proteins. CALML5 undergoes a conformational change as a result of binding calcium. CALML5 is taking part in terminal differentiation of keratinocytes and encodes a calcium binding protein expressed in the epidermis.

Thrombomodulin, also referred to THBD, is an endothelial cell-expressed, transmembrane glycoprotein that can form a complex with the coagulation factor, thrombin. This complex increasethe activation of protein C in the anticoagulant pathway by forming a 1:1 stoichiometric complex with thrombin. Thrombomodulinbound thrombin has procoagulant effect at the same time by inhibiting fibrinolysis by cleaving thrombinactivatable fibrinolysis inhibitor (TAFI) into its active form. Reduced levels of thrombomodulin or increased serum levels of THBD can correlate with pathogenesis of certain cardiovascular diseases, such as atherosclerosis and thrombosis. Furthermore, it associated with, diabetes mellitus, liver cirrhosis, cerebral & myocardial infarction, and multiple sclerosis.

Prolactin-inducible protein (PIP) is a main protein component of benign breast gross cysts. PIP is a famous indicator of breast cancer, since it is found in around 50% of all breast cancer specimens. PIP is expressed in exocrine glands, in pathologic conditions, in breast cysts and breast cancers exhibiting apocrine features. PIP and prostate specific antigen are co-expressed in androgen receptor-positive breast tumours.

Cytokeratin 16, also known as KRT16, is a member of the keratin gene family. KRT16 which acts as a regulator of innate immunity in response to skin barrier breach is required for some inflammatory checkpoint for the skin barrier maintenance. KRT16 is coexpressed with keratin 14 in a few epithelial tissues as esophagus, tongue, and hair follicles.

Complement Factor Properdin (CFP) which is a plasma glycoprotein, is a positive regulator of the alternative complement pathway of the innate immune system. CFP binds and stabilizes the C3- and C5-convertase enzyme complexes in a feedback loop that eventually ends with formation of the membrane attack complex and lysis of the target cell. Mutations in CFP lead to 2 forms of properdin deficiency that cause high susceptibility to meningococcal infections.

The proteasome is a multicatalytic proteinase complex with an extremely organized ring-shaped 20S core structure. The core structure consists of 4 rings of 28 non-identical subunits; 2 rings consist of 7 alpha subunits and 2 rings consist of 7 beta subunits. Proteasomes are spread all over the eukaryotic cells in large quantities and cleave peptides in an ATP/ubiquitin-dependent procedure in a non-lysosomal pathway. A vital role of a modified proteasome, the immunoproteasome, is the handling of class I MHC peptides.

COPZ1 is a member of the adaptor complexes small subunit family. Coatomer is an oligomeric complex which contains as a minimum the alpha, beta, beta', gamma, delta, epsilon and zeta subunits. The zeta subunit has a part in regulating the coat assembly and, therefore, the rate of biosynthetic protein transport due to its association-dissociation properties with the coatomer complex.

Reg protein was shown to be stimulated during the regeneration of pancreatic islets. Since then, many Reg-related proteins have been identified in humans and other animals. In human, the four REG family genes, i.e., REG 1 alpha, REG 1 beta, REG-related sequence (RS) and HIP/PAP, have so far been isolated. These Reg-related proteins are classified into four subfamilies according to their amino-acid sequences, but they share a similar structure and physiological function. Reg protein is a growth factor for pancreatic beta cells and also suggests that the administration of Reg protein could be used as another therapeutic approach for diabetes mellitus. Human REG cDNA which encodes a 166-amino acid protein with a 22-amino acid signal peptide. The amino acid sequence of human REG protein has 68% homology to that of rat Reg protein.
Reg I was found to be expressed mainly in pancreatic beta and acinoductular cells as well as gastric fundic enterochromaffin-like (ECL) cells. Reg I production in ECL cells is stimulated by gastrin, as well as by the proinflammatory cytokine, cytokine-induced neutrophil chemoattractant (CINC)-2Beta. In patients with chronic hypergastrinemia, Reg production is stimulated, with the increased proliferation of gastric mucosal cells. Patients with Helicobacter pylori infection also showed increased Reg production in the gastric mucosa, partly via increased plasma gastrin concentration and partly via increased proinflammatory cytokine production. The serum concentration of the reg-protein was significantly higher in patients with various pancreatic diseases than in normal controls, and was also significantly higher in patients with acute pancreatitis or chronic relapsing pancreatitis than in patients with chronic pancreatitis. Furthermore, the serum PSP/reg-protein concentration was also significantly increased in liver cirrhosis, choledocholithiasis, and various cancers of the digestive system.

Fibronectin takes part in several cellular processes, including tissue repair, embryogenesis, blood clotting, and cell migration/adhesion.Plasma fibronectin level is elevated in severe coronary artery disease. Increased plasma fibronectin levels are related with venous thromboembolism (VTE) particularly in males, and extend the probable association between biomarkers and risk factors for arterial atherothrombosis and VTE. Fibronectin consists in 2 main forms: 1) as an insoluble glycoprotein dimer that serves as a linker in the etracellular matrix and 2) as a soluble disulphide linked dimer found in the plasma. The plasma form is produced by hepatocytes, and the ECM form is synthesized by fibroblasts, chondrocytes, endothelial cells, macrophages, as well as certain epithelial cells. Fibronectin alos takes part as a general cell adhesion molecule by anchoring cells to collagen or proteoglycan substrates. Fibronectin organizes cellular interaction with the ECM by binding to different components of the extracellular matrix and to membrane-bound Fibronectin receptors on cell surfaces.

Matrix metalloproteinase-7 (MMP-7) also known as matrilysin and PUMP (EC 3.4.24.23) cleaves a number of substrates including collagen types IV and X, elastin, fibronectin, gelatin, laminin and proteoglycans. MMP-7 is closely related to the stromelysin family members but is encoded by a different gene. MMP-7 is the smallest of all the MMPs consisting of a pro-peptide domain and a catalytic domain. It lacks the hemopexin-like domain common to other members of the MMPs. MMP-7 is secreted as a 28 kDa proenzyme and can be activated in vitro by organomercurials and trypsin and in vivo by MMP-3 to a 18 kDa active MMP-7 enzyme. Once activated, MMP-7 can activate pro-MMP-1 and pro-MMP-9 but not pro-MMP-2. MMP-7 is widely expressed having been reported in elevated levels in cycling endometrium as well as in colorectal cancers and adenomas, hepatocellular carcinomas, rectal carcinomas, and approximately 50% of gliomas.

Kallikrein-3 (KLK3) belongs to the kallikrein-related peptidase family. Kallikreins are a subgroup of serine proteases having various physiological functions. Numerous kallikreins are involved in carcinogenesis and some may be prospective cancer and other disease biomarkers. Kallikrein-3 is 1 of the 15 kallikrein subfamily members located in a cluster on chromosome 19 and is a protease present in seminal plasma. KLK3 hydrolyzes semenogelin-1 consequently leading to the liquefaction of the seminal coagulum. KLK3 is assumed to act normally in the liquefaction of seminal coagulum, probably by hydrolysis of the high molecular mass seminal vesicle protein. Serum level of the KLK3 protein, called PSA in the clinical setting, is beneficial in the diagnosis and monitoring of prostatic carcinoma.

Streptavidin is a tetrameric protein secreted by Streptomyces avidinii which binds firmly to biotin. Streptavidin is wilyde used in molecular biology through its unique high affinity for the vitamin biotin. The dissociation constant (Kd) of the biotin-streptavidin complex is about ~10-15 mol/L. The strong affinity recognition of biotin and biotinylated molecules has made streptavidin one of the most important components in diagnostics and laboratory kits. The streptavidin/biotin system has one of the biggest free energies of association of yet observed for noncovalent binding of a protein and small ligand in aqueous solution (K_assoc = 10**14). The complexes are also extremely stable over a wide range of temperature and pH.

Based on sequence similarity to VEGF-A, a gene encoding a VEGF homologue has recently been discovered in the genome of Orf virus (OV) (Lyttle et al., 1994). Different isolates of Orf virus show significant amino acid sequence similarity to VEGF-A and described as a viral virulence factor that appears to be derived from captured host genes. All eight cysteine residues of the central cysteine knot motif characteristic of members of the VEGF family are conserved among other residues in the VEGF-E proteins (Dehio et al., 1999; Wise et al., 1999). Alignment of all mammalian VEGF sequences indicated that VEGF-E is distinct from the previously described VEGFs but most closely related to VEGF-A. Like VEGF-A, VEGF-E was found to bind with high affinity to VEGF receptor-2 (KDR) resulting in receptor autophosphorylation, whilst in contrast to VEGF-A, VEGF-E can not bind to VEGF receptor-1 (Flt-1). Furthermore VEGF-E can also not bind to VEGF receptor-3 (FLT-4). Therefore VEGF-E is a potent angiog

Beta-secretase 1 or BACE1 or beta-site amyloid precursor protein cleaving enzyme 1, is a protein that is encoded by the BACE1 gene in humans. Expression of BACE1 is seen primarily in neurons as it is crucial for the creation of myelin sheats in the peripheric nervous system. Beta-secretase 1 is a proteas that is located in the cell membrane (transmembrane). The enzyme consists of 2 active sites (aspartate residues) in the extracellular domain that can act as a dimer.

Methionyl Aminopeptidase 1D (METAP1D) is a part of the peptidase M24A family. METAP1D which is overexpressed in colon cancer cell lines participates in tumorigenesis. METAP1D eliminates methionine from the N-terminus of nascent proteins.