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Phosphoserine aminotransferase (PSAT1) catalyzes the conversion of 3-phosphohydroxypyruvate into 3-phosphoserine which is dephosphorylated consequently by phosphoserine phosphatase to form L-serine. PSAT1 is probably a phosphoserine aminotransferase, based on similarity to proteins in mouse, rabbit, and Drosophila. PSAT1 is expressed at high levels in the brain, liver, kidney and pancreas, and very weakly expressed in the thymus, prostate, testis and colon. Defects in the PSAT1 gene are the cause of phosphoserine aminotransferase deficiency (PSATD). PSATD is distinguished biochemically by low plasma and cerebrospinal fluid concentrations of serine and glycine and clinically by intractable seizures, acquired microcephaly, hypertonia, and psychomotor retardation.

Formiminotransferase cyclodeaminase is an enzyme which catalyzes the conversion of formiminoglutamateand tetrahydrofolateinto formiminotetrahydrofolateand glutamate.
Formiminotransferase cyclodeaminase, a bifunctional enzyme of tetrahydrofolate synthesis, is the target antigen of anti-LC1 (liver cytosol antigen type 1) autoantibodies. Presence of LC1 autoantibodies is a marker for type 2 autoimmune hepatitis (for which anti-LKM 1/cytochrome P450 2D6 autoantibodies are a further marker).
Serum LC1 autoantibody concentrations appear to fluctuate in parallel with aminotransferase levels, a particularly intriguing observation that suggests a possible role of LC1 autoreactivity in the pathogenic mechanism leading to hepatocyte injury.

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.

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.

Progastricsin-C (PGC) is an aspartic proteinase which is synthesized in the gastric mucosa as inactive precursors. PGC is a part of the peptidase family A1 and contains a prosegment which is responsible for stabilizing the inactive form and preventing the entrance of the substrate to the active site. PGC is used as a biomarker for various gastric diseases including Helicobacter pylori related gastritis. PGC is also hydrolyzes various proteins.

BDH1 belongs to the short-chain dehydrogenase/reductase gene family. BDH1 forms a homotetrameric lipid-requiring enzyme of the mitochondrial membrane and has a specific necessity for phosphatidylcholine for optimal enzymatic activity. BDH1 catalyzes the interconversion of acetoacetate and (R)-3-hydroxybutyrate, the 2 main ketone bodies formed during fatty acid catabolism.

NNMT is part of the family of transferases, especially those transferring one-carbon group methyltransferases. NNMT is mostly expressed in the liver, and a lower expression is seen in the kidney, lung, skeletal muscle, placenta and heart. NNMT catalyzes the N-methylation of nicotinamide and other pyridines to form pyridinium ions. This activity is significant for biotransformation of many drugs and xenobiotic compounds. NNMT is accountable for the enzymatic activity which uses S-adenosyl methionine as the methyl donor. NNMT expression is related with tumor stage and DFS time in hepatocellular carcinoma cases. NNMT is a good candidate as a tumor marker of various kinds of cancers. NNMT serum levels have significance in the premature detection and in the management of patients with colorectal cancer.

UROD is the fifth enzyme in the human heme biosynthetic pathway and is in charge for the transfer of uroporphyrinogen to coproporphyrinogen through the deletion of four carboxymethyl side chains. UROD Mutations and deficiency result in 3 autosomal disorders in humans: familial porphyria cutanea tarda (f-PCT), sporadic porphyria cutanea tarda (s-PCT) and hepatoerythropoietic porphyria (HEP).

PRCP is a plasma protein which takes part in the cleavage of C-terminal amino acids linked to proline in proteinfor example angiotensin-2 & 3 at acidic pHenvironment rather than at neutral pHwhich exhibit less activity. This cleavage is important since Angiotensin-2 takes part in regulation of blood pressure & electrolyte balance which is essential to hypertension.

NDUFV3 is one of no less than 41 subunits which form the NADH-ubiquinone oxidoreductase complex that is involved in the mitochondrial respiratory chain and assists in catalyzing the rotenone-sensitive oxidation of NADH and the reduction of ubiquinone. NDUFV3 is 1 of 3 proteins found in the flavoprotein fraction of the complex but it exact function is unknown. Two transcript variants encoding altered isoforms are known for this gene.

DNA polymerase POLL is involved in base excision repair (BER). POLL is a low-fidelity polymerase that takes part in both spontaneous and DNA damage-induced mutagenesis. Furthermore, POLL takes part in the mutagenic bypass of T-T dimers. Pol lambda possesses terminal transferase and 5’-deoxyribose-5-phosphate lyase activity which is synchronized by PCNA and replication protein A.

Aminoacyl-tRNA synthetases are a class of enzymes that charge tRNAs with their cognate amino acids. The protein encoded by this gene is a cytoplasmic enzyme which belongs to the class II family of aminoacyl-tRNA synthetases. The enzyme is responsible for the synthesis of histidyl-transfer RNA, which is essential for the incorporation of histidine into proteins. The gene is located in a head-to-head orientation with HARSL on chromosome five, where the homologous genes share a bidirectional promoter. The gene product is a frequent target of autoantibodies in the human autoimmune disease polymyositis/dermatomyositis.

Carbonic anhydrase (carbonate dehydratase) is a family of metalloenzymes (enzymes that contain one or more metal atoms as a functional component of the enzyme) that catalyze the rapid (and reversible) conversion of carbon dioxide to bicarbonate and protons, a reaction that occurs rather slowly in the absence of a catalyst. Carbonic anhydrase greatly increases the rate of the reaction, with typical catalytic rates of the different forms of this enzyme ranging between 104 and 106 reactions per second. The active site of most carbonic anhydrases contains a zincion. CAIII is a cytoplasmic isoenzyme, but is released into the circulation following injury.

GSTT1 belongs to a superfamily of proteins which catalyze the conjugation of reduced glutathione to a variety of electrophilic and hydrophobic compounds. GSTT1 is one of the GSTs’ four main classes: alpha, mu, pi and theta (which includes GSTT1 and GSTT2). GSTT1 is involved in activation and detoxification reactions and catalyzes the conjugation of industrial chemicals, such as epoxybutane, ethylene oxides, halomethane with glutathione. GSTT1 is found in erythrocytes, at low levels in the liver as well as in Clara and ciliated cells at the alveolar/bronchiolar junction in the lung.
The GSTT1 gene is deficient in 38% of the population. The GSTTI enzyme deficiency might influence the individual risk for development of acquired aplastic anemia and acute myeloid leukemia. The presence or absence of the GSTT1 gene is concurrent with GSST1+ (the conjugator) and GSTT1- (the non-conjugator) phenotypes correspondingly. The GSTT1+ phenotype is able to catalyze the glutathione conjugation of dichloromethane. GSTT1-null genotypes are seen as having a higher risk of developing leukoplakia. Germline genetic polymorphism in GSTT1 is linked to breast cancer.

HEXA is the alpha subunit of the lysosomal enzyme beta-hexosaminidase which, combined with the cofactor GM2 activator protein, catalyzes the degradation of the ganglioside GM2, and other molecules having N-acetyl hexosamines terminus. The two subunits composing Beta-hexosaminidase, alpha and beta, belong to the glycosyl hydrolases family and are encoded by distinct genes. Alpha subunit gene mutations can cause Tay-Sachs disease (GM2-gangliosidosis type I).

Granzyme H also known as GZMH belongs to the peptidase S1 family. GZMH is an essential part for HBV eradication. The HBx protein, which is required for the replication of HBV, is cleaved at Met(79) by GZMH. Furthermore, GZMH inhibitor can abolish GZNH- as well as lymphokine-activated killer cell-mediated HBx degradation and HBV clearance. A HBx-deficient HBV is resistant to GzmH- in addition to lymphokine-activated killer cell-mediated viral clearance.

Glutaminyl-Peptide Cyclotransferase, also known as QPCT is a member of the glutaminyl-peptide cyclotransferase family. QPCT is responsible for the biosynthesis of pyroglutamyl peptides. Furthermore, QPCT is partial against acidic and tryptophan residues adjacent to the N-terminal glutaminyl residue and a lack of importance of chain length following the second residue. QPCT catalyzes N-terminal pyroglutamate formation, also in vitro, it catalyzes pyroglutamate formation of N-terminally truncated form of APP amyloid-beta peptides [Glu-3]-beta-amyloid.

DHPS is vital for the first step of hypusine biosynthesis. DHPS catalyzes the NAD-dependent transfer of the butylamine moiety of spermidine to the epsilon-amino group of a specific lysine residue of the EIF5A precursor protein to form the intermediate deoxyhypusine residue.

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.

Creatine Kinase BB is a cytoplasmic enzyme involved in energy homeostasis. The encoded protein reversibly catalyzes the transfer of phosphate between ATP and various phosphogens such as creatine phosphate. It acts as a homodimer in brain as well as in other tissues, and as a heterodimer with a similar muscle isozyme in heart. The encoded protein is a member of the ATP:guanido phosphotransferase protein family. A pseudogene of this gene has been characterized.

IMPDH2 is a member of the IMPDH/GMPR family. IMPDH2 catalyzes the NAD-dependent oxidation of inosine-5'-monophosphate into xanthine-5'-monophosphate, which is afterward converted into guanosine-5'-monophosphate. IMPDH2 is the rate-limiting enzyme in the de novo guanine nucleotide biosynthesis. IMPDH2 is consequently involved in maintaining cellular guanine deoxy- and ribonucleotide pools required for DNA and RNA synthesis. In addition, IMPDH1 and IMPDH2 are targets for the important immunosuppressive drug, MPA. Furthermore, the IMPDH2 gene is up-regulated in some neoplasms, suggesting it may have a role in malignant transformation.

MMP-1 (interstitial collagenase) can break down a wide range of substrates including types I, II, III, VII, VIII, and X collagens as well as L-Selectin, pro-TNF, IL-1?, IGFBP-3, IGFBP-5, casein, gelatin, ?1 antitrypsin, myelin basic protein, pro-MMP2 and pro-MMP9. A significant function of MMP-1 is the degradation of fibrillar collagens in extracellular matrix remodeling. MMP-1 is expressed in fibroblasts, keratinocytes, endothelial cells, monocytes and macrophages. MMP1 can be divided into a number of distinct domains: a prodomain which is cleaved on activation, a catalytic domain containing the zinc binding site and a short hinge region with a carboxyl terminal domain. MMP1 is part of a cluster of MMP genes which localize to chromosome 11q22.3.

Chitinase is a digestive enzyme which breaks down glycosidic bonds in chitin. Due to chitin being a component of the cell walls of fungi and exoskeletal elements of some animals (including worms and arthropods), chitinases are usually found in organisms that either need to remake their own chitin or to dissolve and digest the chitin of fungi or animals. Chitinivorous organisms include many bacteria genuses such as Aeromonas, Bacillus, Vibrio, among others, which may be pathogenic or detritivorous. Chitinase expression is mediated by the NPR1 gene and the salicylic acid pathway, both of which are involved in resisting fungal and insect attack. Human chitinases appear in gastric juices. They are likely to be digestive chitinases, for catabolic activity. Chitinase activity is identified systemically in humans, in the blood, and possibly cartilage. Chitinase has been related to allergies, asthma in particular has been linked to enhanced chitinase expression levels, also dust mites and mold spores which are both chitin covered.

PNP is a member of the PNP/MTAP phosphorylase family of proteins. PNP catalyzes the reversible phosphorolysis of ribonucleosides and 2’-deoxyribonucleosides with specificity for guanine, hypoxanthine and their analogs. PNP deficiency is a rare autosomal recessive genetic disease linked to a severe defect in T-lymphocyte function and neurologic disorder in children, comprising four percent of combined immunodeficiency cases.