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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.

Aminoacyl-tRNA synthetases are a class of enzymes which charge tRNAs with their cognate amino acids. Asparaginyl-tRNA synthetase (NARS) is localized to the cytoplasm and is a member of the class II family of tRNA synthetases. The N-terminal domain characterizes the signature sequence for the eukaryotic asparaginyl-tRNA synthetases.

Tyrosyl-tRNA synthetase (YARS2) is a mitochondrial protein which catalyzes the attachment of tyrosine to tRNA(Tyr) in a two-step reaction: tyrosine is first activated by ATP to form Tyr-AMP and afterward transferred to the acceptor end of tRNA(Tyr). YARS2 gene mutations are linked with myopathy with lactic acidosis and sideroblastic anemia type 2 (MLASA2).

Diphthamide biosynthesis protein 2 (DPH2) is a homodimer and each of its monomers can bind a [4Fe-4S] cluster. DPH2 is the target of ADP ribosylating diphtheria toxin (DT) and Pseudomonas exotoxin A (PE). DPH2 was identified by its ability to complement a diphthamide mutant strain, and thus serves in diphthamide biosynthesis. The loss of DPH2 pre-activates NF-kB and death receptor pathways and renders MCF7 cells hypersensitive to tumor necrosis factor.

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.

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.

Lysyl-tRNA synthetase (KARS) is a member of the class-II aminoacyl-tRNA synthetase family. KARS exists as both mitochondrial and cytoplasmic isoforms produced by alternative splicing, and believed to have a role in autoimmune diseases, such as polymyositis or dermatomyositis. The KARS protein functions to catalyze the aminoacylation of tRNAs by their corresponding amino acids, so linking amino acids with tRNA-contained nucleotide triplets.

Poly (ADP-Ribose) Polymerase 2 (PARP2) contains a catalytic domain which is homologous to that of poly (ADP-ribosyl) transferase but lacks an N-terminal DNA binding domain which activates the C-terminal catalytic domain of poly (ADP-ribosyl) transferase. PARP2 is capable of catalyzing a poly (ADP-ribosyl)ation reaction. The basic residues within the N-terminal area of this protein can bear potential DNA-binding properties, and can be engaged in the nuclear and/or nucleolar targeting of the protein. There has been found two alternatively spliced transcript variants encoding distinct isoforms.

Molybdenum Cofactor Synthesis 2 (MOCS2) is a heterotetrameric synthase comprised of 2 small (MOCS2A) and 2 large (MOCS2B) subunits. Both the large and small subunits of molybdopterin synthase are encoded from the MOCS2 gene by overlapping open reading frames. MOCS2 operates in the second step of the molybdenum cofactor or molybdopterin (MPT) synthesis. MOCS2 catalyzes the formation of MPT from precursor Z by incorporating a dithiolene functional group.

Acyl-CoA synthetase family member 2, also known as ACSF2 is a member of the ATP-dependent AMP-binding enzyme family. Acyl-CoA synthetases are a family of enzymes which catalyze the thioesterification of fatty acids with coenzymeA to form activated intermediates, which play a basic part in lipid metabolism as well as homeostasis of lipid-related processes. ACSF2 is required for the complex of lipid synthesis, energy production via beta-oxidation, protein acylation and fatty-acid dependent transcriptional regulation. Moreover, ACSF2 is required for fatty acid import into cells by the process of vectorial acylation.

Alanyl-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 108 kDa protein is an autoantigen recognized by PL-12 antibodies which occur in a subset of patients with polymyositis and dermatomyositis. Preliminary data suggest that epitope spreading occurs in the autoimmune PL-12 response such that even antibodies to an isolated alanyl-tRNA molecule can develop.

MTHFS is a cytosolic protein which takes part in the formate metabolic process. MTHFS along with a magnesium cofactor catalyzes the ATP-dependent reaction which reduces 5-formyltetrahydrofolate (5-MTHF) to 5,10-methenyltetrahydrofolate(MTHF). MTHF is the substrate used by MTHFR (methylenetetrahydrofolate reductase) to generate 5-MTHF. In addition, MTHF is a coenzyme used in thymidine biosynthesis by thymidylate synthase (FAD).

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.

AASDHPPT is a member of the P-Pant transferase superfamily. AASDHPPT catalyzes the post-translational modification of target proteins by phosphopantetheine and can transfer the 4'-phosphopantetheine moiety from coenzyme A to a serine residue of a broad range of acceptors, such as the acyl carrier domain of FASN (in vitro). AASDHPPT is similar to Saccharomyces cerevisiae LYS5, which is required for the activation of the alpha-aminoadipate dehydrogenase in the biosynthetic pathway of lysine. AASDHPPT is found in the heart, skeletal muscle, placenta, testis, brain, pancreas, liver and kidney. It’s been suggested that defects in the human AASDHPPT gene result in pipecolic acidemia.

OAS1 enzyme is a member of the 2’,5’-oligoadenylate synthetase family. OAS1 is induced by interferons and uses adenosine triphosphate in 2’-specific nucleotidyl transfer reactions to synthesize 2’,5’-oligoadenylates(2-5As). These molecules in turn activate latent RNase L resulting in viral RNA degradation and the inhibition of viral replication.
OAS1 may have a role in mediating resistance to virus infection, control of cell growth, differentiation, and apoptosis. OAS1 binds double-stranded RNA and polymerizes ATP into PPP (A2'P5'A)N oligomers, which activate the latent RNase L that, once activated, cleaves single-stranded RNAs.
OAS1 gene mutations are been linked to host susceptibility to viral infection.
OSA1 gene polymorphisms are linked to the outcome of hepatitis C virus infection. Furthermore, OAS1 gene polymorphisms are linked to the susceptibility to severe acute respiratory syndrome.

Rhodanese is a mitochondrial matrix enzyme that is encoded by the nucleus. Rhodanese is involved in cyanide detoxification, the formation of iron-sulfur proteins, and the modification of sulfur-containing enzymes. Rhodanese catalyzes the chemical reaction of thiosulfate & cyanide to sulfite & thiocyanate (detoxification). Rhodanese is part of the transferase family of proteins. Rhodanese includes two highly conservative domains, identified as rhodanese homology domains. In mammals, the majority of cyanide is converted to thiocyanate. Rhodanese has weak mercaptopyruvate sulfurtransferase activity.

ATPase Transporting Lysosomal Accessory Protein 2 (ATP6AP2) is a protein associated with triphosphatases (ATPases). Proton-translocating ATPases have vital roles in energy conservation, secondary active transport, acidification of intracellular compartments, and cellular pH homeostasis. ATP6AP2 is linked with the transmembrane sector of the V-type ATPases, which have a transmembrane proton-conducting sector and an extramembrane catalytic sector. ATP6AP2 serves as a renin and prorenin cellular receptor; it mediates renin-dependent cellular responses by activating ERK1 and ERK2. ATP6AP2 is expressed in the brain, heart, placenta, liver, kidney and pancreas. ATP6AP2 is hardly detectable in the lung and skeletal muscles. ATP6AP2 is also expressed in the vascular structures and by syncytiotrophoblast cells in the mature fetal placenta.

Threonyl-tRNA synthetase, cytoplasmic (TARS) is a member of the class-II aminoacyl-tRNA synthetase family. The main role of TARS is in tRNA aminoacylation. The N-terminal domain of the TARS enzyme is responsible for the competition with the ribosome whereas the catalytic and the C-terminal domain are involved in binding the 2 anticodon arm-like structures in the operator.

DYNLL1 is a protein that cooperates with NOS1 causing NOS1 inhibition. Binding of DYNLL1 weakens NOS1 (Neuronal nitric oxide synthase) dimer, a conformation needed for activity, and it regulates several biologic processes through its effects on nitric oxide synthase activity. DYNLL1 is a ubiquitously expressed protein that demonstrates high expression in testis and moderate expression in brain.

KLF3 belongs to the Sp1-like/KLF family. KLFs is a family of evolutionarily conserved zinc finger-having transcription factors with various regulatory purposes in cell growth, embryogenesis, proliferation and differentiation. KLF3 is Kruppel-like zinc finger which contain transcription factors and take part in hematopoiesis.

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).

BPGM is found at high concentrations in red blood cells where it binds to and decreases the oxygen affinity of hemoglobin. PGM deficiency increases the oxygen affinity of cells. BPGM is a multifunctional enzyme that catalyzes 2,3-DPG synthesis through its synthetase activity, and 2,3-DPG degradation using its phosphatase activity. BPGM has phosphoglycerate phosphomutase activity. Mutations in BPGM cause hemolytic anemia. BPGM catalyzes the reaction of EC 5.4.2.1 (mutase) and EC 3.1.3.13 (phosphatase), but with a reduced activity.

HAAO is a monomeric cytosolic protein which is a member of intramolecular dioxygenases family containing nonheme ferrous iron. The HAAO protein catalyzes the synthesis of quinolinic acid (QUIN) from 3-hydroxyanthranilic acid. QUIN is an excitotoxin whose toxicity is facilitated by its ability to activate glutamate N-methyl-D-aspartate receptors. Amplified cerebral levels of QUIN may contribute to the pathogenesis of neurologic and inflammatory disorders. HAAO is widely distributed in peripheral organs, such as liver and kidney, and is also present in low amounts in the central nervous system.

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.