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Celiac disease is an enteropathy that is characterized by intestinal lesions of variable severity. Tissue-type transglutaminase (tTG) is believed to be the predominant autoantigen for celiac disease and the corresponding autoantibodies show higher sensitivity and specificity than anti-gliadin antibodies. Highly pure recombinant human tTG is now available to replace the traditionally used tTG fraction from guinea pig.
Tissue-type transglutaminase antigens have been specifically modified for improved handling: exchange of an active site amino acid eliminates the protein cross-linking activity of the enzyme, while maintaining the native three-dimensional structure and the enzyme's secondary GTPase activity. This engineering assures reproducible properties of the antigen preparations through the absence of variable and ill-defined covalent aggregates of tTG antigen and host cell proteins.

Fucosyltransferase 3 (FUT3) catalyzes alpha-1, 3 and alpha-1, 4 glycosidic linkages which take part in the expression of Vim-2, Lewis A, Lewis B, sialyl Lewis X and Lewis X/SSEA-1 antigens. FUT3 takes part in blood group Lewis determination; Lewis-positive (Le+) individuals have an active enzyme while Lewis-negative (Le-) individuals have an inactive enzyme. FUT3 also operates on the corresponding 1, 4-galactosyl derivative, creating1, 3-L-fucosyl links.

G3BP1 belongs to the heterogeneous nuclear RNA-binding proteins and is also an element of the Ras signal transduction pathway. G3BP1 is one of the DNA-unwinding enzymes that favors partially unwound 3'-tailed substrates and is also able to unwind partial RNA/DNA and RNA/RNA duplexes in an ATP-dependent fashion. G3BP1 binds specifically to the Ras-GTPase-activating protein by associating with its SH3 domain. In addition, G3BP1 cleaves exclusively between cytosine and adenine and cleaves MYC mRNA preferentially at the 3'-UTR.

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.

TPI1 is one of the triosephosphate isomerase family. TPI1 catalyzes the isomerization of glyceraldehydes 3-phosphate (G3P) and dihydroxy-acetone phosphate (DHAP) in glycolysis and gluconeogenesis. Mutations in TPI1 causes triosephosphate isomerase deficiency (TPI deficiency). TPI deficiency is an autosomal recessive disorder which is the most severe clinical disorder of glycolysis and is related to neonatal jaundice, chronic hemolytic anemia, progressive neuromuscular dysfunction, cardiomyopathy and increased susceptibility to infection.

MTHFD2 plays a role as a homodimer which requires magnesium and inorganic phosphate. MTHFD2 has a pseudogene on chromosome 7 and owns 3 different enzymatic activities. Each of the activities catalyzes 1 of 3 sequential reactions in the interconversion of 1-carbon derivatives of tetrahydrofolate, which are substrates for methionine, thymidylate, and de novo purine syntheses.

HTATIP2 is part of the short-chain dehydrogenases/reductases (SDR) family which acts as a tumor suppressor in metabolic suppression, inhibition of angiogenesis and induces the expression of apoptosis related genes Bad and Siva. HTATIP2 cooperates with the activation domain of HIV-1 TAT and enhances its transcription by phosphorylating RNA polymerase II (Pol II). Defects in HTATIP2 are related with hepatocellular carcinomas and apoptotic resistant tumor cells, implicating a probable use for HTATIP2 in antitumor therapy.

Deoxyuridine Triphosphatase (DUT) is a ubiquitous enzyme that functions in nucleotide metabolism. Deoxyuridine Triphosphatase, in the presence of magnesium ions, is responsible for hydrolyzing dUTP to dUMP and diphosphate. This reaction is imperative for keeping the intracellular dUTP concentration low so that uracil does not become incorporated into DNA. Extensive integration of uracil into DNA can eventually lead to cell death. This suggests that DUT is crucial for cell viability, further implying that it is a prospective target for anticancer therapy.

Phosphatidylinositol transfer protein alpha (PITPNA) is found in the cytoplasm, where it catalyzes the transfer of phosphatidylinositol (PI) and phosphatidylcholine (PC) between membranes. PITPNA belongs to a family of lipid-binding proteins which transfer molecules of phosphatidylinositol or phosphatidylcholine between membrane surfaces. PITPNA is implicated in phospholipase C signaling and in the production of phosphatidylinositol 3, 4, 5-trisphosphate (PIP3) by phosphoinositide-3-kinase.

3-ketodihydrosphingosine reductase (KDSR) is a 332 amino acid multi-pass membrane protein which localizes to the ER and is a member of the short-chain dehydrogenases/reductases (SDR) family. KDSR is a secreted protein that is weakly expressed in hematopoietic tissue. Furthermore, KDSR catalyzes the reduction of 3-ketodihydrosphingosine (KDS) to dihydrosphingosine (DHS). The putative active site residues of KDSR are found on the cytosolic side of the endoplasmic reticulum membrane. Chromosomal rearrangement in the KDSR gene is a cause of follicular lymphoma, aka type II chronic lymphatic leukemia.

Beta-lactamase is a type of enzyme (EC 3.5.2.6) produced by some bacteria that is responsible for their resistance to beta-lactam antibiotics like penicillins, cephalosporins, cephamycins and carbapenems. These antibiotics have a common element in their molecular structure: a four-atom ring known as a beta-lactam. The lactamase enzyme breaks that ring open, deactivating the molecule's antibacterial properties.

CBR4 is a member of the short-chain dehydrogenase/reductase family. CBR4 has a role in biosynthesis of fatty acids in the mitochondria and a broad substrate specificity and reduces 9,10-phenanthrenequinone, 1,4-benzoquinone and a range of other o-quinones and p-quinones (in vitro). CBR4 formation of a heteroteramer with HSD17B8 has NADH-dependent 3-ketoacyl-acyl carrier protein reductase activity for o- and p-quinones.

ATP-dependent Clp protease proteolytic subunit (CLPP) is a member of the peptidase family S14. CLPP cleaves peptides in a variety of proteins in a manner which requires ATP hydrolysis. CLPP being the catalytic core of the Clp proteolytic complex is commonly involved in many cellular processes via the regulation of intracellular protein quality. CLPP is responsible for a somewhat general and central housekeeping function rather than for the degradation of specific substrates.

Glutamyl endopeptidase (GLU-C) is an enzyme which cleaves peptide bonds on the carboxyl-terminal side of glutamic acid and, less frequently, aspartic acid (for example: Glu-|-Xaa, Asp-|-Xaa). GLU-C is a pathogenic factor involved in the adherence and colonization of human tissue. GLU-C preferentially cleaves peptide bonds on the carboxyl-terminal side of aspartate and glutamate. GLU-C is required for proteolytic maturation of thiol protease SspB and inactivation of SspC, an inhibitor of SspB. GLU-C is the most important protease for degradation of fibronectin-binding protein (FnBP) and surface protein A, which are involved in adherence to host cells. Furthermore, GLU-C protects bacteria against host defense mechanism by cleaving the immunoglobulin classes IgG, IgA and IgM. GLU-C may also be involved in the stability of secreted lipases.

HPSE also known as Heparanase-1 is an enzyme which cleaves heparan sulfate proteoglycans to allow cell movement through changing the extracellular matrix. In fact, the Heparan sulfate proteoglycans are major components of the basement membrane and extracellular matrix. In addition, this cleavage can release bioactive molecules from the extracellular matrix. HPSE is significant for the overall degradation of proteins in lysosomes.

Aspartoacylase is a homodimer which catalyzes the deacetylation of N-acetylaspartic acid (NAA) (a protein whose hydrolysis is crucial to maintenance of intact white matter) to generate acetate and L-aspartate. Aspartoacylase (ASPA) is expressed in the liver, lung and kidney tissue, as well as in the skeletal muscle and in cerebral white matter. NAA is ample in the brain where hydrolysis by aspartoacylase is believed to aid maintain white matter. In other tissues ASPA functions as a scavenger of NAA from body fluids. ASPA gene mutations cause Canavan disease (CAND or spongy degeneration of the brain).

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.

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-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.

AKR7A2 participates in the detoxification of aldehydes and ketones. AKR7A2 catalyzes the NADPH-dependent reduction of succinic semialdehyde to gamma-hydroxybutyrate. AKR7A2 is involved in producing the neuromodulator gamma-hydroxybutyrate (GHB). AKR7A2 has extensive substrate specificity. AKR7A2 shows NADPH-dependent aldehyde reductase activity towards 2-carboxybenzaldehyde, 2-nitrobenzaldehyde and pyridine-2-aldehyde (in vitro). AKR7A2 reduces 1,2-naphthoquinone and 9,10-phenanthrenequinone (in vitro). AKR7A2 reduces the dialdehyde protein-binding form of aflatoxin B1 (AFB1) to the non-binding AFB1 dialcohol. AKR7A2 takes part in protection of liver against the toxic and carcinogenic effects of AFB1, a potent hepatocarcinogen.

Uridine 5'-monophosphate synthase (UMPS), is a bifunctional enzyme that catalyzes the ultimate two steps of the de novo pyrimidine biosynthetic pathway. UMPS in eukaryotes links the orotate phosphoribosyltransferase and the orotidine-5’-monophosphate (OMP) decarboxylase activities into a single protein. The harmony of these 2 enzymes is assumed to be stabilized the catalytic centers as a result of the low molar concentration of the protein in mammalian cells.mutations in this gene are the reason of inherited orotic aciduria disease.

WARS is part of the class I tRNA synthetase family. 2 types of tryptophanyl tRNA synthetase exist, a cytoplasmic form, called WARS, and a mitochondrial form, called WARS2. WARS catalyzes the aminoacylation of tRNA(trp) with tryptophan and is induced by INF. WARS controls ERK, Akt, and eNOS activation pathways that are related with angiogenesis, cytoskeletal reorganization and shear stress-responsive gene expression.

TEV protease is the common name for the 27 kDa catalytic domain of the Nuclear Inclusion a (NIa) protein encoded by the tobacco etch virus (TEV). Because its sequence specificity is far more stringent than that of factor Xa, thrombin, or enterokinase, TEV protease is a very useful reagent for cleaving fusion proteins. TEV protease recognizes a linear epitope of the general form E-Xaa-Xaa-Y -Xaa-Q-(G/S), with cleavage occurring between Q and G or Q and S. The most commonly used sequence is ENLYFQG.

Heparanase is an endo β-D-glucuronidase, which degrades heparan sulfate side chains of heparan sulfate proteoglycans (HSPGs) in the extracellular matrix. Heparanase plays an important role in ECM degradation, facilitating the migration and extravasation of tumor cells and inflammatory leukocytes (1,2,3). Upon degradation, heparanase releases growth factors and cytokines that stimulate cell proliferation and chemotaxis (4,5). Heparanase is a heterodimer comprised of a 50 kDa subunit harboring the active site and a 8 kDa subunit. It is produced as a latent 65 kDa precursor and proteolytically processed to its active form (1,6). Heparanase is highly expressed in myeloid leukocytes (i.e. neutrophils) in platelets and in human placenta. Human heparanase was found to be upregulated in various types of primary tumors, correlating in some cases with increased tumor invasiveness and vascularity and with poor prospective survival (7,8).