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TDO2 is a ferrous heme enzyme that catalyzes the first and rate-limiting step in the kynurenine pathway which is the major pathway of tryptophan metabolism. TDO2 integrates oxygen into the indole moiety of tryptophan. TDO2 has broad specificity towards tryptamine and derivatives including D- and L-tryptophan, 5-hydroxytryptophan and serotonin.

Serine/threonine-protein kinase 16 (STK16) is a membrane-associated protein kinase which phosphorylates on serine and threonine residues. STK16 is involved in secretory vesicle trafficking or intracellular signaling. Furthermore, the STK16 protein may have a role in regulating stromal-epithelial interactions which occur during ductal morphogenesis in the mammary gland. STK16 can autophosphorylate on Tyr residue; it is however unclear whether STK16 has tyrosine-protein kinase toward other proteins. STK16 may also be involved in TGF-beta signaling.

Polymerase III Polypeptide F (POLR3F) is a member of the eukaryotic RPC34/RPC39 RNA polymerase subunit family. POLR3F is DNA-dependent RNA polymerase which catalyzes the transcription of DNA into RNA using the 4 ribonucleoside triphosphates as substrates. POLR3F is one of many subunits forming eukaryotic RNA polymerase III (RNA Pol III), which transcribes 5S ribosomal RNA and tRNA genes. POLR3F binds both TFIIIB90 and TBP, 2 subunits of RNA polymerase III transcription initiation factor IIIB (TFIIIB).

M2 autoantigen is a key mark of antimitochondrial autoantibodies (AMA), a typical serological feature in patients suffering from primary biliary cirrhosis (PBC) which is a serious autoimmune liver disease accompanied by damage to intrahepatic bile ducts. Molecular definition of the M2 antigen has displayed it as no less than 3 separate target proteins. The M2 role is like the so-called E2 subunits (or dihydrolipoamide transferases) of different mitochondrial dehydrogenase complexes:
*pyruvate dehydrogenase complex.
*branched chain 2-oxo-acid dehydrogenase complex.
*2-oxoglutarate dehydrogenase complex.
Biochemically, these complexes catalyze the oxidative decarboxylation of various alpha-keto-acid substrates and systematically engage with a prosthetic lipoamide group; they are situated in the mitochondrial matrix in association with the inner membrane. The most well-known reactivity of AMA positive PBC sera is against PDC-E2. Some patients have AMA which reacts with PDC-E2 alone (95%), but most patients also show reactivity against OGDC-E2 (39-88%) and/or BCOADC-E2 (53-55%). Actually, patients can be found with reactivity only against OGDC-E2 and/or BCOADC-E2 and no PDC-E2 autoantibodies. These patients will be overlooked in assays based on natural source-derived, predominantly PDC-E2-containing M2 antigen preparations.

SAE1 and SAE2 form heterodimers which take part in the posttranslational modification of proteins (sumoylation). This process regulates protein structure as well as intracellular localization of the target. SAE1/SAE2 may indicate on dermatomyositis (DM) as autoantibodies against those 2 proteins have been found in patients.

Abhydrolase domain-containing protein 10 (ABHD10) is a member of the AB hydrolase superfamily.

Antioxidant enzyme Glutathione S- Transferase (GST) is thought to do the primary cellular defense mechanism against reactive oxygen species. GST reduces lipid hydroperoxides through its Se-independent glutathione peroxidase activity. The enzyme also detoxifies lipid peroxidation end products such as 4-hydroxynonenal (4-HNE).
The soluble GST is a 26 kDa protein which occurs as a dimer in all aerobic organisms. Each monomer has two domains, one that binds GSH and is an /-structure similar to thioredoxin and the other, all helical, that binds the hydrophobic substrate. The GST -fusion protein expression system is a widely used recombinant protein expression system that allows a peptide or a regulatory protein domain to be expressed as a fusion to the C-terminus of Schistosoma japonicum GST. Fusion proteins also possess GST -enzymatic activity and can undergo dimerization similar to in vivo. The fusion protein can be purified via GST -affinity column chromatography. In most cases, the desired peptides or domains are removed from GST by applying a specific protease that recognizes and cleaves the linker between the protein domain and GST. The technique has been widely used to generate different kinds of proteins for crystallization, molecular immunology studies, the production of vaccines and studies involving protein-protein and protein-DNA interactions.

Dual Specificity Phosphatase 22, also known as DUSP22, is a part of the protein-tyrosine phosphatase family which holds 1 tyrosine-protein phosphatase domain. DUSP22 activates the Jnk signaling pathway and dephosphorylates and deactivates p38 and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK). DUSP22 interacts with MAPK1 and MAPK8.

Protein disulfide isomerases (PDIs) constitute a family of structurally related enzymes which catalyze disulfide bonds formation, reduction, or isomerization of newly synthesized proteins in the lumen of the endoplasmic reticulum (ER). They act also as chaperones, and are, therefore, part of a quality-control system for the correct folding of the proteins in the same subcellular compartment. PDI has been found to have moderate effects (25-fold) on the rate of oxidative folding of proteins in vitro.
Recombinant Human Protein Disulfide Isomerase is involved in disulphide-bond formation and isomerization, as well as the reduction of disulphide bonds in proteins. Recombinant PDI has been found to have moderate effects (25-fold) on the rate of oxidative folding of proteins in vitro.

DUSPs are distinguished by their ability to dephosphorylate both tyrosine and serine/threonine residues. DUSPs have been implicated as major modulators of critical signaling pathways. Dual specificity phosphatase 19 (DUSP19) belongs to the dual specificity protein phosphatase subfamily. DUSP19 is a protein phosphatase which functions as a stress-activated protein kinase pathway-regulating phosphatase. DUSP19 contains a variation of the consensus DUSP C-terminal catalytic domain, with the last serine residue replaced by alanine, and lacks the N-terminal CH2 domain found in the MKP class of DUSPs.

BAT1 belongs to the DEAD box family of RNA-dependent ATPases that mediate ATP hydrolysis during pre-mRNA splicing. UAP56 protein is a vital splicing factor which is needed for connecting U2 small nuclear ribonucleoprotein with pre-mRNA, as well as takes a key part in mRNA export from the nucleus to the cytoplasm. Mutations in this protein may be connected to rheumatoid arthritis.

Carbohydrate Sulfotransferase 3 (CHST3) belong to sulfotransferase 1 family which iincludes 14 enzymes that all members are Golgi-localized type II membrane proteins. These enzymes utilizes 3'-phospho-5'-adenylyl sulfate (PAPS) as sulfonate donor to catalyze the transfer of sulfate to position 6 of the N-acetylgalactosamine (GalNAc) residue of chondroitin. CHST3 can also sulfate Gal residues of keratan sulfate and Gal residues in sialyl N-acetyllactosamine (sialyl LacNAc) oligosaccharides. CHST3 is expressed in heart, placenta, skeletal muscle and pancreas. CHST3 takes part in maintenance of naive T-lymphocytes in the spleen.

Putative peptidyl-tRNA hydrolase PTRHD1 (PTRHD1) is a 140 amino acid protein, which is encoded by a gene located on human chromosome 2p23.3. Chromosome 2 is the second largest human chromosome; it consists of 237 million bases, encodes over 1,400 genes and makes up approximately 8% of the human genome. Several genetic diseases are linked to genes on chromosome 2.

Glutathione S-transferase Mu 2 (GSTM2) belongs to the glutathione s-transferase (GST) family of proteins. GSTM2 is a glutathione S-transferase that belongs to the mu class. There are 8 families of GST proteins, specifically: alpha, kappa, mu, omega, pi, sigma, theta and zeta, each of which is composed of proteins that have various functions throughout the cell. The mu class of enzymes functions in the detoxification of electrophilic compounds, including carcinogens, therapeutic drugs, environmental toxins and products of oxidative stress, by conjugation with glutathione. The genes encoding the mu class of enzymes are structured in a gene cluster on chromosome 1p13.3 and are proven to be highly polymorphic. These genetic variants can change an individual''s susceptibility to carcinogens and toxins as well as have an effect on the toxicity and efficacy of several drugs.

Glutathione S-transferase A4 (GSTA4) is a member of the GST superfamily. The GSTA4 enzyme is involved in cellular defense against toxic, carcinogenic, and pharmacologically active electrophilic compounds. GSTA4 shows an especially high activity with reactive carbonyl compounds such as alk-2-enals. GSTA4 is extremely effective in catalyzing the conjugate addition of reduced glutathione to 4-hydroxynonenal, which is an important product of peroxidative degradation of arachidonic acid and a frequently used biomarker for oxidative damage in tissue. The GSTA4 enzyme is expressed at a high level in the brain, placenta, and skeletal muscle and much lower in the lung and liver.

DUSP23 is a member of the protein-tyrosine phosphatase family. DUSP23 is a protein phosphatase which facilitates dephosphorylation of phosphorylated proteins on Tyr and Ser/Thr residues. In vitro, DUSP23 dephosphorylate p44-ERK1 (MAPK3) but not p54 SAPK-beta (MAPK10). In addition, DUSP23 enhances activation of JNK and p38(MAPK14).

Glutathione S-transferase mu 5 (GSTM5) belongs to the glutathione s-transferase (GST) family of proteins. There are 8 families of GST proteins, specifically alpha, kappa, mu, omega, pi, sigma, theta and zeta, each of which is comprised of proteins which have various functions throughout the cell. GSTM5 belongs to the mu class of enzymes which function in the detoxification of electrophilic compounds, including carcinogens, therapeutic drugs, environmental toxins and products of oxidative stress, by conjugation with glutathione. GSTM5 has an imperative role in detoxification. GSTM5 conjugates reduced glutathione to a large number of exogenous and endogenous hydrophobic electrophiles.

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.

Thymidine Kinase 1 (TK1) is a phosphotransferase (a kinase): 2'-deoxythymidine kinase, ATP-thymidine 5'-phosphotransferase. TK1 is present in 2 forms in mammalian cells, TK1 and TK2. Thymidine kinases hold a main function in the synthesis of DNA and thus in cell division, as they are part of the distinctive reaction chain to introduce deoxythymidine (present in the body fluids as a result of degradation of DNA from food and from dead cells) into the DNA. Thymidine kinase is necessary for the action of many antiviral drugs. Thymidine kinase is used to select hybridoma cell lines in production of monoclonal antibodies.

Trypsin inhibitor SPINK1 is secreted from pancreatic acinar cells into pancreatic fluid. SPINK1 has a role in inhibition of trypsin-catalyzed premature initiation of zymogens in the pancreas and the pancreatic duct. Alterations in SPINK1 gene are the cause for tropical calcific and pancreatitis hereditary pancreatitis.

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.

Dual Specificity Phosphatase 26 (DUSP26) inhibits MAP kinase p38 by dephosphorylating it and inhibits p38-mediated apoptosis in anaplastic thyroid cancer cells. DUSP26 also induces activation of MAP kinase p38 and c-Jun N-terminal kinase. DUSP26 inactivates MAPK1 and MAPK3 which leads to dephosphorylation of heat shock factor protein 4 and a decrease in its DNA-binding activity.

ITPA enzyme catalyzes the pyrophosphohydrolysis of both ITP (inosine triphosphate) and dITP (deoxyinosine triphosphate) to IMP (inosine monophosphate) and diphosphate. IMP is exercised as a substrate for purine nucleotide pathways. IMP is phosphorylated to ITP, and ITPA mediates the concentration of ITP in the cell by changing ITP back to IMP. Defects in ITPA result in ITPA deficiency which is thought to be inherited and is characterized by an over-accumulation of ITP in erythocytes, leukocytes and fibroblasts.