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DNA toposisomerase I is a key nuclear enzyme that interconverts supercoiled DNA to the required topological conformations for normal DNA replication and transcription. This enzyme is the target antigen for the so-called Scl-70 autoantibodies. Scl-70 antibodies are a specific marker in Scleroderma patients (specificity 98-100%) and are associated with the presence of diffuse skin involvement and pulmonary fibrosis.
In human tissues the DNA topoisomerase I is initially synthesized as a protein with 100 kDa molecular weight. Most of this precursor is then proteolytically processed to a species with 70 kDa molecular weight from which the Scl-70 antigen has derived its name.

PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and accelerate the folding of proteins. Cyclophilin-A is a cyclosporin binding-protein and may play a role in cyclosporin A-mediated immunosuppression. Cyclophilin-A can also interact with several HIV proteins, including p55 gag, Vpr, and capsid protein, and has been shown to be necessary for the formation of infectious HIV virions. Multiple pseudogenes that map to different chromosomes have been reported.

Cyclophilin-G is a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and speeds up the protein folding. PPIG catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and is involved in the folding, transport, and assembly of proteins. PPIG is localized to the nuclear speckles, a nuclear compartment rich in splicing factors, and cooperates with the splicing factors SC35 and pinin. Cyclophilin-G also takes part in the regulation of pre-mRNA splicing.

TOP1 is an important nuclear enzyme that interconverts supercoiled DNA to the necessary topological conformations for standard DNA replication and transcription. TOP1 is the target antigen for TOP1 autoantibodies. TOP1 antibodies are a specific marker in scleroderma patients (specificity 98-100%) and are related with the existence of diffuse skin involvement and pulmonary fibrosis. In human tissues top1 enzyme is primarily synthesized as a protein with a molecular weight of 100-kDa. Most of this precursor is then proteolytically processed to a 70-kDa size, from which the TOP1 antigen has derived its name.

Cyclophilin-D is a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and speeds up the protein folding. Cyclophilin-D possess PPIase activity and binds to the immunosuppressant cyclosporin-A. Cyclophilin-D is very well known that its overexpression suppresses the apoptosis in cancer cell. Cyclophilin-D suppresses apoptotic cell death by the use of mitochondrial hexokinase-2 dependent mechanism in cancer cells.

Peptidylprolyl Isomerase C (PPIC) belongs to the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and hasten the folding of proteins. Like other PPIases, PPIC binds immunosuppressant cyclosporin A.

Cyclophilin-E is a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and speeds up the protein folding. Cyclophilin-E contains a highly conserved cyclophilin domain in addition to a RNA-binding domain. Cyclophilin-E exhibits PPIase activity, protein folding activities and possess RNA-binding activity. Cyclophilin-E contains 2 RNA binding domains at the N-terminal region and a PPIase domain at the C-terminal region.

FKBP1A is a 12kDa protein initially discovered on an immune cells on the basis of its capability to bind as well as mediate the intracellular effect of the immunosuppressant FK506. FKBP1A is also known to mediate the action of Rapamycin-immunosuppressive agent. FKBP1A is part of the family of immunophilins, which have in common high affinity for immunosuppressant drugs and a peptidyl-prolyl cis-trans isomerase (PPIase). Activity which participates in folding of proline-containing protein. In the absence of immunosuppressive ligands, FKBP1A is involved in intracellular calcium regulation by associating with 3 types of Ca2+ release channel complexes: skeletal ryanodine receptors, cardiac ryanodine receptors and the inositol 1,4,5-triphosphate receptor. FKBP1A also interact with TGF-beta type I receptor exerting an inhibitory effect on the TGF-beta signaling pathway. FKBP12 plays a role in modulation of ryanodine receptor isoform-1 (ryr-1), a component of the calcium release channel of skeletal muscle sarcoplasmic reticulum. FKBP1A increase the folding of proteins and catalyzes the cis-trans isomerization of proline imidic peptide bonds in oligopeptides.

Glucose-6-phosphate isomerase (GPI) is a part of the GPI family whose members encode multifunctional phosphoglucose isomerase proteins involved in energy pathways. GPI is a dimeric enzyme which catalyzes the reversible isomerization of glucose-6-phosphate and fructose-6-phosphate. Mammalian GPI also functions as a tumor-secreted cytokine and an angiogenic factor (AMF) which stimulates endothelial cell motility. In addition, GPI is a neurotrophic factor (Neuroleukin) for spinal and sensory neurons. GPI performs in different capacities inside and outside the cell. In the cytoplasm, GPI is involved in glycolysis and gluconeogenesis, while outside the cell it acts as a neurotrophic factor for spinal and sensory neurons.
Defects in the GPI gene cause the nonspherocytic hemolytic anemia and a severe enzyme deficiency can be linked to hydrops fetalis, immediate neonatal death and neurological impairment.

PDIA3 is an enzyme that belongs to the endoplasmic reticulum and interacts with lectin chaperones calreticulin and calnexin to modulate folding of newly synthesized glycoproteins. PDIA3 has protein disulfide isomerase activity. Complexes of lectins and PDIA3 mediate protein folding by promoting formation of disulfide bonds in their glycoprotein substrates. PDIA3 is expressed in the lumbar spinal cord from rats submitted to peripheral lesion during neonatal period. PDIA3 interacts with thiazide-sensitive sodium-chloride cotransporter in the kidney and is induced by glucose deprivation. PDIA3 is part of the major histocompatibility complex (MHC) class I peptide-loading complex (TAP1), which is important for formation of the final antigen conformation and export from the endoplasmic reticulum to the cell surface.

Cyclophilin-D is a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and speeds up the protein folding. Cyclophilin-D possess PPIase activity and binds to the immunosuppressant cyclosporin-A. Cyclophilin-D is very well known that its overexpression suppresses the apoptosis in cancer cell. Cyclophilin-D suppresses apoptotic cell death by the use of mitochondrial hexokinase-2 dependent mechanism in cancer cells.

Cyclophilin B (also known as PPIB, peptidylpropyl isomerase B) is a cyclosporine-binding protein and is mainly located within the endoplasmic reticulum. It is associated with the secretory pathway and released in biological fluids. This protein can bind to cells derived from T- and B-lymphocytes, and may regulate cyclosporine A-mediated immunosuppression.

Cyclophilin B (also known as PPIB, peptidylpropyl isomerase B) is a cyclosporine-binding protein and is mainly located within the endoplasmic reticulum. It is associated with the secretory pathway and released in biological fluids. This protein can bind to cells derived from T- and B-lymphocytes, and may regulate cyclosporine A-mediated immunosuppression.

FKBP2 is part of the immunophilin protein family, which takes part in immunoregulation and basic cellular processes involving protein folding and trafficking. FKBP2 is a cis-trans prolyl isomerase that binds the immunosuppressants FK506 and rapamycin. FKBP2 functions as an ER chaperone and as a component of membrane cytoskeletal scaffolds.

Disulfide Oxidoreductase or DsbA is a protein, found in the plasma. It is part of the thioredoxin protein family. The protein creates disulfide bonds in the target proteins by contributing disulfide bond from its Cys30-Pro31-His32-Cys33 active site to a couple of cysteine residues.

Cyclophilin-D is a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family. PPIases catalyze the cis-trans isomerization of proline imidic peptide bonds in oligopeptides and speeds up the protein folding. Cyclophilin-D possess PPIase activity and binds to the immunosuppressant cyclosporin-A. Cyclophilin-D is very well known that its overexpression suppresses the apoptosis in cancer cell. Cyclophilin-D suppresses apoptotic cell death by the use of mitochondrial hexokinase-2 dependent mechanism in cancer cells.

GNPDA1, catalyzes the conversion of glucosamine-6-phosphate to fructose-6-phosphate, a reaction that under physiological conditions proceeds to the formation of fructose-6-phosphate. GNPDA1 is widely expressed with highest expression in testes, ovary and heart. GNPDA1 triggers calcium oscillations in mammalian eggs. These oscillations are as the necessary trigger for egg activation and early development of the embryo.

FKBP3 is part of a family of immunosuppressant receptors which inhibit T-cell proliferation by arresting two distinct cytoplasmic signal transmission pathways. FKBP3 accelerates the folding of proteins. FKBP3 is part of the immunophilin protein family, which participates in immunoregulation and fundamental cellular processes concerning protein folding and trafficking. FKBP3 is a cis-trans prolyl isomerase enzyme that binds the immunosuppressants FK506 and rapamycin, as well as histone deacetylases, the transcription factor YY1, casein kinase II, and nucleolin. It has a greater affinity for rapamycin than for FK506 and therefore is a significant protein for immunosuppression by rapamycin.

SURA is a PPIase enzyme and chaperone of Escherichia coli and other Gram-negative bacteria. SURA is a key player in the biogenesis of beta-barrel outer membrane proteins and is involved in cell envelope homeostasis and cell envelope functions. SURA is necessary for the survival of E.coli in stationary phase and needed for pilus biogenesis.

Peptidyl-prolyl cis-trans isomerase-like 3 (PPIL3) belongs to the cyclophilin family which catalyzes the cis-trans isomerization of peptidylprolyl imide bonds in oligopeptides. PPIL3 acts either as catalyst or as molecular chaperone in protein-folding events.

Human Pin 1 is a peptidyl-prolyl cis/trans isomerase (PPIase) that interacts with NIMA and essential for cell cycle regulation Pin1 is nuclear PPIase containing a WW protein interaction domain, and is structurally and functionally related to Ess1/Ptf1, an essential protein in budding yeast. PPIase activity is necessary for Ess1/Pin1 function in yeast. Pin1 is thus an essential PPIase that regulates mitosis presumably by interacting with NIMA and attenuating its mitosis-promoting activity. Substrates of Pin1 include the mitotic regulators (Cdc25 phosphatase and NIMA, PLK I, Wee, and Myt1 kinases), several transcription factors like b-Catenin, c-Jun, and the tumor suppressor protein p53, and some specific proteins like the RNA Pol II, the cytoskeleton protein tau, and the G1/S protein Cyclin D1.

GSTZ1 is part of the glutathione S-transferase super-family which encodes multifunctional enzymes vital in the detoxification of electrophilic molecules, including carcinogens, mutagens, and several therapeutic drugs, by conjugation with glutathione. GSTZ1 participates in the catabolism of phenylalanine and tyrosine. Thus defects in GSTZ1 cause harsh metabolic disorders including alkaptonuria, phenylketonuria and tyrosinaemia. GSTZ1 is a bifunctional protein which has minimal glutathione-conjugating activity with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole and maleylacetoacetate isomerase activity. GSTZ1 has low glutathione peroxidase activity with T-butyl and cumene hydroperoxides. GSTZ1 catalyzes the glutathione dependent oxygenation of dichloroacetic acid to glyoxylic acid.

Pin 1 is a peptidyl-prolyl cis/trans isomerase (PPIase) which interacts with NIMA and essential for cell cycle regulation Pin1 is nuclear PPIase containing a WW protein interaction domain, and is structurally and functionally related to Ess1/Ptf1, an essential protein in budding yeast. PPIase activity is necessary for Ess1/Pin1 function in yeast. Pin1 is thus an essential PPIase that regulates mitosis presumably by interacting with NIMA and attenuating its mitosis-promoting activity. Substrates of Pin1 include the mitotic regulators (Cdc25 phosphatase and NIMA, PLK I, Wee, and Myt1 kinases), several transcription factors like b-Catenin, c-Jun, and the tumor suppressor protein p53, and some specific proteins like the RNA Pol II, the cytoskeleton protein tau, and the G1/S protein Cyclin D1.

IMPA2 is a member of the inositol monophosphatase family. IMPA2 catalyzes the dephosphoylration of inositol monophosphate and has a significant role in phosphatidylinositol signaling. IMPA2 can use the myo-inositol monophosphates, scylloinositol 1,4-diphosphate, glucose-1-phosphate, beta-glycerophosphate, and 2'-AMP as substrates. IMPA2 is a pharmacological target for lithium Li(+) action in brain. IMPA2 is considered to have a role in schizophrenia and bipolar disorder.