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Threonyl-tRNA Synthetase is a member of the aminoacyl-tRNA synthetase family, key enzymes of protein biosynthesis which charge tRNA molecules with the respective amino acids. This 83 kDa protein is an autoantigen recognized by PL-7 antibodies which occur in a subset of patients with polymyositis and dermatomyositis. Preliminary data suggest that PL-7 antibodies (similar to Jo-1 antibodies) indicate an increased risk for lung involvement, but this needs to be confirmed for a larger number of cases.

GLUL catalyzes the synthesis of glutamine from glutamate and ammonia. Glutamine is a major source of energy and that takes part in cell proliferation, inhibition of apoptosis, and cell signaling. GLUL is expressed during early fetal stages, and has a role in maintaining body pH by removing ammonia from circulation. Mutations in GLUL gene are related with congenital glutamine deficiency.

GOT1 is a pyridoxal phosphate-dependent enzyme which exists in cytoplasmic and mitochondrial forms, GOT1 and GOT2, which participate in amino acid metabolism and the urea and tricarboxylic acid cycles. Both enzymes are homodimeric and show close homology.

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.

Tyrosyl-tRNA synthetase (YARS) is a member of the class I tRNA synthetase family. YARS is a vital enzyme which catalyzes the aminoacylation of tRNATrp with tryptophan, a critical function of the cell’s protein synthesis machinery. Expression of YARS is highly stimulated in human cells by the addition of IFN-gamma.

Glutathione synthetase (GSS) is the second enzyme in the glutathione biosynthesis pathway. GSS catalyses the condensation of gamma-glutamylcysteine and glycine to form glutathione. Defects in the GSS are the cause of glutathione synthetase deficiency aka GSS deficiency or 5-oxoprolinuria or pyroglutamic aciduria, which is a severe form characterized by an increased rate of hemolysis and defective function of the central nervous system.

Adenosine Kinase is an abundant enzyme in mammalian tissues which catalyzes the transfer of the gamma-phosphate from ATP to adenosine, thus is as a regulator of concentrations of both extracellular adenosine and intracellular adenine nucleotides. Adenosine has extensive effects on the cardiovascular, nervous, respiratory, and immune systems and inhibitors of the enzyme take a crucial pharmacological part in growing intravascular adenosine concentrations and acting as anti-inflammatory agents.

UDP Glycosyltransferase 8 (UGT8) is a member of the UDP-glycosyltransferase family. UGT8 catalyzes the transfer of galactose to ceramide, a crucial enzymatic step in the biosynthesis of galactocerebrosides, which are abundant sphingolipids of the myelin membrane of the central nervous system and peripheral nervous system.

Farnesyl-Diphosphate Farnesyltransferase 1, also known as FDFT1 is a membrane-associated enzyme sited at a branch point in the mevalonate pathway. FDFT1belongs to the phytoene/squalene synthase family. FDFT1 is the 1st specific enzyme in cholesterol biosynthesis, which catalyzes the dimerization of 2 molecules of farnesyl diphosphate in a two-step reaction to form squalene.

NAT1 is a member of the arylamine N-acetyltransferase family. NAT1 catalyzes N- or O-acetylation of heterocyclic and arylamine substrates in the detoxification of a large number of drugs. Several alleles triggering high levels of N-acetyltransferase activity were linked to colon and urinary bladder cancers, since NAT1 also bioactivate numerous known carcinogens. NAT1 aids metabolize drugs and other xenobiotics, and takes part in the detoxification of a plethora of hydrazine and arylamine drugs.

GOT2 is a pyridoxal phosphate-dependent enzyme which is found in cytoplasmic and inner-membrane mitochondrial forms, GOT1 and GOT2. GOT2 is invloved in amino acid metabolism and the urea and tricarboxylic acid cycles. The 2 enzymes are homodimeric and demonstrate close homology.

PCYT2 is a member of the cytidylyltransferase family. PCYT2 is an enzyme which catalyzes the formation of CDP-MEA from CTP and phospho MEA in the Kennedy pathway of phospholipid synthesis. PCYT2 has the strongest expression in the liver, heart, and skeletal muscle.

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.

AK1 is a small ubiquitous enzyme which is essential for maintenance and cell growth. It is involved in the regulation of adenine nucleotide composition within a cell by catalyzing the reversible transfer of the terminal phosphate group between ATP and AMP. The AK1 protein is found in the cytosol of skeletal muscle, brain and erythrocytes. Defects in the AK1 gene are the cause of a form of hemolytic anemia.

Cytochrome c oxidase assembly factor 4 (COA4) is the last enzyme of the mitochondrial respiratory chain which needs a great number of accessory factors. COA4 is vital for oxidative phosphorylation and comprises multiple complexes including cytochrome c oxidase, assembled in macromolecular supercomplexes. COX4 is a protein-coding gene which defect in it causes an acute human encephalomyopathies.

N-alpha-acetyltransferase 50 (NAA50) consists of 169 amino acid cytoplasmic protein belonging to the acetyltransferase family and GNAT subfamily. NAA50 is a likely catalytic component of the ARD1A-NARG1 complex which displays alpha acetyltransferase activity. NAA50 has also been shown to interact with MAK10 and is encoded by a gene that maps to human chromosome 3q13.2.

2-Enoyl-Coenzyme A (CoA) Hydratase, Beta (HADHB) is the beta subunit of the mitochondrial trifunctional protein, that catalyzes the last 3 phases of mitochondrial beta-oxidation of long chain fatty acids. HADHB binds RNA and reduces the stability of various mRNAs. Mutations in HADHB cause trifunctional protein deficiency.

Hematopoietic Prostaglandin D Synthase (HPGDS) belongs to the sigma class glutathione-S-transferase family. The HPGDS enzyme catalyzes the conversion of PGH2 to PGD2 and has a role in the production of prostanoids in the immune system and mast cells. The presence of the HPGDS enzyme can be utilized to identify the differentiation stage of human megakaryocytes. Furthermore, HPGDS is a prostaglandin involved in smooth muscle contraction/relaxation and an effective inhibitor of platelet aggregation, and the conjugation of glutathione with a extensive range of aryl halides and organic isothiocyanates. In addition, HPGDS displays low glutathione-peroxidase activity towards cumene hydroperoxide. HPGDS is expressed in a number of megakaryocytic cell lines but not in platelets. HPGDS is highly expressed in the adipose tissue, macrophages and placenta; however it is expressed at lower levels in the lung, heart, lymph nodes, appendix, bone marrow and fetal liver.

SHMT1 is a member of the SHMT family. SHMT1 is the cellular form of serine hydroxymethyltransferase, a pyridoxal phosphate-containing enzyme which catalyzes the reversible conversion of serine and tetrahydrofolate to glycine and 5 10-methylene tetrahydrofolate. In addition, SHMT1 specifically provides one-carbon units for thymidylate biosynthesis, reduces methylenetetrahydrofolate pools for S-adenosylmethionine (SAM) synthesis by synthesizing serine, sequesters 5-methyltetrahydrofolate and inhibits SAM synthesis.

FARSB, also known as Phenylalanyl-TRNA Synthetase Beta is a member of the phenylalanyl-tRNA synthetase beta subunit family. FARSB is composed tetramer of two alpha and two beta subunits. In the presence of ATP, this tetramer is accountable for attaching L-phenylalanine to the terminal adenosine of the appropriate tRNA.

NUDT2 belongs to the MutT family of nucleotide pyrophosphatases, a subset of the larger NUDIX hydrolase family. NUDT2 conserves homeostasis by using water to cleave the metabolite NUDT symmetrically back into its original ATP and AMP molecules. In addition, NUDT2 is active towards other adenosine and diadenosine polyphosphates with four or more phosphate groups, however, not towards diadenosine triphosphate. NUDT2 has a role in heat shock and metabolic stress by regulating intracellular dinucleoside polyphosphate concentrations.

Thymidine phosphorylase precursor (TYMP) is a platelet-derived endothelial cell growth factor that catalyzes the formation of thymine and 2-deoxy-D-ribose-1-phosphate from thymidine and orthophosphate. TYMP is an angiogenic inducer that potently stimulates the growth of endothelial cells and induces chemotaxis. TYMP has a highly restricted target cell specificity acting only on endothelial cells. An increased expression of TYMP is found in a broad array of different solid tumors and inflammatory diseases and is frequently associated with poor prognosis. Mutations in the TYMP gene are linked to mitochondrial neurogastrointestinal encephalomyopathy.

HPRT1 has a main part in the generation of purine nucleotides through the purine salvage pathway. HPRT1 primarily functions to salvage purines from degraded DNA to renewed purine synthesis. Therefore, it performs as a catalyst in the reaction between guanine and phosphoribosyl pyrophosphate to form GMP.

Translational activator of mitochondrially encoded cytochrome c oxidase I (TACO1) belongs to the TACO1 family. TACO1 is a mitochondrial protein which functions as a translational activator of mitochondrially-encoded cytochrome c oxidase 1. Mutations in this gene are associated with Leigh syndrome.