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Sulfite oxidase, also known as SUOX is a homodimeric protein localized to the intermembrane space of mitochondria. Each subunit includes a heme domain as well as a molybdopterin-binding domain. The SUOX enzyme catalyzes the oxidation of sulfite to sulfate, the last reaction in the oxidative degradation of the sulfur amino acids cysteine and methionine. In addition, the deficiency of SUOX results in neurological abnormalities which are often fatal at an early age.

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.

Single-Stranded DNA Binding Protein 1 (SSBP) participates in mitochondrial biogenesis. SSBP binds preferentially and cooperatively to ss-DNA. The SSBP protein is involved in mitochondrial DNA replication and associates with mitochondrial DNA.

ALDH2 is part of the aldehyde dehydrogenase family of proteins which catalyze the chemical transformation from acetaldehyde to acetic acid. ALDH2 is the second enzyme of the major oxidative pathway of alcohol metabolism. ALDH2 has 2 major liver isoforms: cytosolic and mitochondrial, which differ by their electrophoretic mobilities, kinetic properties, and subcellular localizations. Nearly all Caucasians have 2 major isozymes, whereas roughly 50% of Orientals have only the cytosolic isozyme, omitting the mitochondrial isozyme. The extremely higher rate of acute alcohol intoxication with Orientals compared to Caucasians is due to the fact of the absence of mitochondrial isozyme. ALDH2 has a low Km for acetaldehydes, and is localized in mitochondrial matrix.

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.

NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 5 (NDUFA5) is a member of the complex I NDUFA5 subunit family. The human NDUFA5 gene codes for the B13 subunit of complex I of the respiratory chain that transfers electrons from NADH to ubiquinone. The NDUFA5 protein localizes to the inner mitochondrial membrane as part of the seven component-containing, water soluble 'iron-sulfur protein' (IP) fraction of complex I, even though its exact role is undetermined.

ACAT2 enzyme participates in lipid metabolism. ACAT2 takes part in lipoprotein assembly, catalyzing cholesterol esterification in mammalian cells. ACAT2 is an integral membrane protein that localizes to the endoplasmic reticulum of human intestinal cells. ACAT2 deficiency contributes to severe mental retardation and hypotonus.

DARS uses a 2 step reaction to catalyze the specific attachment of an amino acid to its cognate tRNA: the amino acid (AA) is first activated by ATP to form AA-AMP and then transferred to the acceptor end of the tRNA.

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.

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).

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.

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.

PRDX5 belongs to the peroxiredoxin family of antioxidant enzymes, which reduce hydrogen peroxide and alkyl hydroperoxides with reducing equivalents supplied through the thioredoxin system. PRDX5 has an antioxidant protective function in different tissues under normal conditions and during inflammatory processes. Peroxiredoxin-5 interacts with peroxisome receptor 1 and is involved in intracellular redox signaling. PRDX5 is involved in intracellular redox signaling. Peroxiredoxin-5 is a significant antioxidant protein of lung epithelial cells for its expression in the human lung increases during inflammation. PRDX5 expression is upregulated in osteoarthritis. PRDX5 may be significant in mitochondrial genome stability. Peroxiredoxin-5 has a protective role in human tendon cells against oxidative stress by reducing apoptosis and upholding collagen synthesis.

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.

Glycylpeptide N-tetradecan-oyltransferases 2 (NMT2) is a cytoplasmic protein which is a member of the NMT family of proteins. The proteins in the NMT family catalyze the addition of a myristoyl group to the N-terminal glycine residue of eukaryotic, fungal and viral proteins. These proteins are mostly detected in the heart, gut, kidney, liver and placenta. NMT catalyzes the reaction of N-terminal myristoylation of various signaling proteins. NMT transfers myristic acid from myristoyl coenzyme A to the amino group of a protein's N-terminal glycine residue. There are several distinct NMTs which vary in the molecular weight and /or subcellular distribution.

PTGES2 is a membrane-associated prostaglandin E synthase, which catalyzes the conversion of prostaglandin H2 to prostaglandin E2. Additionally, PTGES2 activates the transcription regulated by a gamma-INF-activated transcription element. PTGES2 is widely expressed- in the heart, including apex, inter-ventricular septum, both atria and ventricles, but not in the aorta. PTGES2 is also expressed in fetal heart. PTGES2 is detected in various regions of the brain: cerebellum; occipital, frontal and parietal lobes. It is also expressed in the lymph nodes, skeletal muscle, kidney and trachea, but not in the thymus or lung. PTGES2 is overexpressed in colorectal cancer.

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.

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.

PYCR1 is a universal housekeeping enzyme which catalyzes the NAD(P)H-dependent conversion of pyrroline-5-carboxylate to proline. PYCR1 enzyme also takes a physiologic part in the generation of NADP(+) in certain cell types. PYCR1 forms a homopolymer and localizes to the mitochondrion. Mutations in PYCR1 are the source of cutis laxa autosomal recessive type 2B (ARCL2B).

PDK1 takes part in the regulation of enzymatic activity of mammalian pyruvate dehydrogenase which is part of a mitochondrial multienzyme complex to catalyze the oxidative decarboxylation of pyruvate and is one of the major enzymes responsible for the regulation of homeostasis of carbohydrate fuels in mammals. PDK1 inhibits glioblastoma growth. PDK1 inhibits the mitochondrial pyruvate dehydrogenase complex by phosphorylation of the e1 alpha subunit, therefore contributing to the regulation of glucose metabolism. PDK1 kinase activity is negatively regulated by binding to 14-3-3.

NDUFS4 is a subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I), the primary multi-subunit enzyme complex of the mitochondrial respiratory chain. Complex I is involved in cellular ATP production, the main source of energy for numerous vital processes in living cells. NDUFS4 removes electrons from NADH and passes them by a series of diverse protein-coupled redox centers to the electron acceptor ubiquinone. NDUFS4 presents a hotspot of mutations in the genetic apparatus of oxidative phosphorylation and the correct assembly of the subunit it encodes is essential for completion of the assembly of complex I.

Pyruvate Dehydrogenase Complex, Component X, also known as PDHX, encodes the E3 binding protein subunit of the PDH complex which contains 3 catalytic subunits. PDHX tethers E3 dimers to the E2 core of the pyruvate dehydrogenase complexes of eukaryotes. This specific binding is critical for a functional PDH complex.

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.

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.