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Translocase of Inner Mitochondrial Membrane 8 Homolog A (TIMM8A) takes part in the import and insertion of hydrophobic membrane proteins from the cytoplasm into the mitochondrial. TIMM8A plays a role as a chaperone-like protein which protects the hydrophobic precursors from aggregation and leads them through the mitochondrial intermembrane space. TIMM8A is essential for the transfer of beta-barrel precursors from the TOM complex to the sorting and assembly machinery (SAM complex) of the outer membrane. Defects in TIMM8A cause Jensen syndrome. TIMM8A and TIMM13, forms a 70 kDa heterohexamer.

Branched Chain Amino-Acid Transaminase 2 (BCAT2) is a member of the class-IV pyridoxal-phosphate-dependent aminotransferase family. BCAT2 is a branched chain aminotransferase found in mitochondria. BCAT2 forms a dimer which catalyzes the first step in the production of the branched chain amino acids leucine, isoleucine, and valine. In addition, BCAT2 may actn as a transporter of branched chain alpha-keto acids.

Mitochondrial Ribosomal Protein L1 (MRPL1) exists as a component of the 39S ribosomal subunit and operates in conjunction with other MRPs to mediate protein synthesis. Mitochondrial ribosomes consist of a large 39S subunit and a small 28S subunit, both of which are consist of multiple mitochondrial ribosomal proteins (MRPs) that are encoded by nuclear genes and are vital for protein synthesis within mitochondria. MRPL1 exists as 2 isoforms produced by alternative splicing. Isoform 1 of MRPL1 is ubiquitously expressed while isoform 2 is particularly expressed in heart.

CKMT1A is in charge of the transfer of high energy phosphate from mitochondria to the cytosolic carrier, creatine. CKMT1A is a member of the creatine kinase isoenzyme family and exists as two isoenzymes, sarcomeric MtCK and ubiquitous MtCK, encoded by separate genes. Mitochondrial creatine kinase arises in two different oligomeric forms: dimers and octamers, unlike the exclusively dimeric cytosolic creatine kinase isoenzymes. Numerous malignant cancers with poor prognosis have displayed overexpression of ubiquitous mitochondrial creatine kinase which is linked to high energy turnover and inability to remove cancer cells through apoptosis.

Creatine Kinase, Mitochondrial 2 (CKMT2) is a member of the ATP:guanido phosphotransferase family. CKMT2 is responsible for the transfer of high energy phosphate from mitochondria to the cytosolic carrier, creatine. CKMT2 reversibly catalyzes the transfer of phosphate between ATP and various phosphogens (e.g. creatine phosphate). Creatine kinase isoenzymes have a principal role in energy transduction in tissues with large, variable energy demands, such as skeletal muscle, heart, brain and spermatozoa. Mitochondrial creatine kinase occurs in 2 different oligomeric forms: dimers and octamers, contrary to the exclusively dimeric cytosolic creatine kinase isoenzymes. The CKMT2 gene contains sequences homologous to a number of motifs which are shared among some nuclear genes encoding mitochondrial proteins and therefore may be crucial for the coordinated activation of these genes during mitochondrial biogenesis.

Apoptosis-Inducing Factor, Mitochondrion-Associated, 1 (AIFM1) is a mitochondrial protein which translocates to the nucleus once apoptosis has been initiated. AIFM1 causes DNA fragmentation and chromatin condensation and also triggers the release of cytochrome c and caspase-9 from mitochondria. Bcl-2 overexpression prevents the release of AIFM1 from mitochondria, but doesn’t block its apoptogenic activity.

APRT is part of the purine/pyrimidine phosphoribosyltransferase family. APRT enzyme catalyzes the formation of AMP and inorganic pyrophosphate from adenine and 5-phosphoribosyl-1-pyrophosphate (PRPP). APRT produces adenine as a by-product of the polyamine biosynthesis pathway. A homozygous deficiency in APRT causes 2,8-dihydroxyadenine urolithiasis. APRT catalyzes a salvage reaction resulting in the formation of AMP.

Phenylalanyl-tRNA synthetase 2 mitochondrial (FARS2) is a member of the class II aminoacyl- tRNA synthetase family. FARS2 is a mitochondrial matrix protein. FARS2 when acting as a monomer, catalyzes the ATP-dependent conversion of L-phenylalanine and tRNA (Phe) to L-phenlalanyltRNA (Phe), an event which is vital for proper translation and protein expression.

MTHFD2 plays a role as a homodimer which requires magnesium and inorganic phosphate. MTHFD2 has a pseudogene on chromosome 7 and owns 3 different enzymatic activities. Each of the activities catalyzes 1 of 3 sequential reactions in the interconversion of 1-carbon derivatives of tetrahydrofolate, which are substrates for methionine, thymidylate, and de novo purine syntheses.

CKMT1A is in charge of the transfer of high energy phosphate from mitochondria to the cytosolic carrier, creatine. CKMT1A is a member of the creatine kinase isoenzyme family and exists as two isoenzymes, sarcomeric MtCK and ubiquitous MtCK, encoded by separate genes. Mitochondrial creatine kinase arises in two different oligomeric forms: dimers and octamers, unlike the exclusively dimeric cytosolic creatine kinase isoenzymes. Numerous malignant cancers with poor prognosis have displayed overexpression of ubiquitous mitochondrial creatine kinase which is linked to high energy turnover and inability to remove cancer cells through apoptosis.

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.

NADH dehydrogenase [ubiquinone] 1 alpha subcomplex assembly factor 4 (NDUFAF4) is involved in the compilation of mitochondrial NADH: ubiquinone oxidoreductase complex (complex I). In addition, NDUFAF4 is involved in cell proliferation and survival of hormone-dependent tumor cells. NDUFAF4 may also be a regulator of breast tumor cell invasion. NDUFAF4 gene mutations cause the mitochondrial complex I deficiency.

ASS1 is involved in the urea cycle, which is a sequence of chemical reactions that is localized in liver cells. The urea cycle processes excess nitrogen that is generated as the body uses proteins. The surplus nitrogen is used to create a molecule called urea, which is excreted from the body in urine.

Mitochondrial Ribosome Recycling Factor (MRRF) is a member of the RRF family. MRRF attaches to the large ribosomal subunit in the cleft which has a peptidyl transferase center. MRRF controls the release of ribosome from messenger RNA at the termination of protein biosynthesis. Also, it may intensify the efficacy of translation by recycling ribosome from one round of translation to another.

6-PyruvoylTetrahydropterin Synthase is part of the family of lyases, specifically those carbon-oxygen lyases acting on phosphates. 6-PyruvoylTetrahydropterin Synthase catalyzes the elimination of inorganic triphosphate from dihydroneopterin triphosphate, which is the second and irreversible step in the biosynthesis of tetrahydrobiopterin from GTP. Tetrahydrobiopterin, is a necessary cofactor and regulator of a range of enzyme activities, including enzymes involved in serotonin biosynthesis and NO synthase activity. Mutations in 6-PyruvoylTetrahydropterin Synthase gene result in hyperphenylalaninemia.

Transcription Factor B2, Mitochondrial (TFB2M) is an S-adenosyl-L-methionine-dependent methyltransferase which specifically dimethylates mitochondrial 12S rRNA at the conserved stem loop. In addition, TFB2M is essential for basal transcription of mitochondrial DNA, most likely via its interaction with POLRMT and TFAM. TFB2M promotes transcription independently of the methyltransferase activity. TFB2M like TFB1M, activates transcription of mitochondrial DNA more effectively, whilst having less methyltransferase activity.

GMP synthase (GMPS) is involved in purine biosynthesis. GMPS, which is a homodimer, catalyzes the last step in the GMP synthesis pathway, specifically the ATP-dependent amination of XMP to GMP. GMPS is comprised of one GMP-binding domain and one glutamine amidotransferase type-1 domain through which it communicates its catalytic activity. GMPS is engaged in the de novo synthesis of nucleotides which are not only vital for DNA and RNA synthesis, but also supply GTP, which is involved in sevral cellular processes important for cell division. GMPS gene chromosomal translocations are linked with acute myeloid leukemias, suggesting a possible role for GMPS in carcinogenesis.

ME2 catalyzes the oxidative decarboxylation of malate to pyruvate, malat + NAD(P)+? pyruvate + CO2 + NAD(P)H+, and is found both in eukaryotic and prokaryotic cells. Three different isoforms of ME are known to be in mammalian tissues: a strictly cytosolic NADP+-dependent enzyme, an NADP+-dependent mitochondriail isoform, and a mitochondrial isoenzyme that is able to use both NAD+ and NADP+ but is more effective with NAD+. The mammalian isoforms size is about 62-64 kDa. A native size of 240,000 Da proposes a tetrameric structure for the active enzyme.
Mitochondrial NAD+-dependent ME 2 activity is seen in tissues that experience many cell divisions, like spleen, thymus, and the basal cells of the small intestinal mucosa. ME2 is also expressed all through the rapid cleavage stages of early Xenopus development. Activity for this isoform is low or nonexistent in brain, muscle, and normal and regenerating liver tissue from rat but was observed in rat adrenal cortex, pigeon and human skeletal muscle, and in heart muscle of some species. In addition, it is expressed in mitochondria of all tumor cells inspected to detain ascites tumors, hepatoma cells, and a variety of other tumors and transformed cell lines.

Thymidylate synthase catalyzes the methylation of deoxyuridylate to deoxythymidylate using 5,10-methylenetetrahydrofolate as a cofactor which maintains the dTMP (thymidine-5-prime monophosphate) pool vital for DNA replication and repair. Thymidylate synthase plays an important role as a cancer chemotherapeutic agent. Thymidylate synthase is the primary site of action for 5-fluorouracil, 5-fluoro-2-prime-deoxyuridine, and several folate analogs.

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.

Asparagine synthetase (ASNS) is a cytoplasmic enzyme that turns aspartate toasparagine and functions mostly in mammalian organs. ASNS is responsible for cell growthand its mRNA content is associated with changes in the cell cycle. ASNS may also play a role as a biomarker for ovarian cancer.

Cytochrome c oxidase subunit VB (COX5B) is the terminal enzyme of the mitochondrial respiratory chain. COX5B is a multi-subunit enzyme complex which couples the transfer of electrons from cytochrome c to molecular oxygen and contributes to a proton electrochemical gradient across the inner mitochondrial membrane. There are two isoforms of COX5:COX5a and COX5b. Transcription of COX5A (the aerobic isoform) is up-regulated as the rate of cellular respiration increases, when oxygen levels within the cell are high. However, when oxygen levels are low, COX5B (the hypoxic isoform) transcription increases and functions to maximize the turnover rate of the COX apoenzyme.

Uridine 5'-monophosphate synthase (UMPS), is a bifunctional enzyme that catalyzes the ultimate two steps of the de novo pyrimidine biosynthetic pathway. UMPS in eukaryotes links the orotate phosphoribosyltransferase and the orotidine-5’-monophosphate (OMP) decarboxylase activities into a single protein. The harmony of these 2 enzymes is assumed to be stabilized the catalytic centers as a result of the low molar concentration of the protein in mammalian cells. Mutations in UMPS are the reason of inherited orotic aciduria disease.

HIBCH enzyme is in charge of hydrolysis of both HIBYL-CoA and beta-hydroxypropionyl-CoA. Damages in the HIBCH gene linked to 3-hyroxyisobutyryl-CoA hydrolase deficiency. Multiple transcript variants exist as a result of alternative splicing.