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ATP5H is a member of the ATPase d subunit family and encodes the d subunit of the F0 complex. Electron transport complexes of the respiratory chain create a proton gradient across the membrane which induces ATP5H to transform ADP to ATP. Two alternatively spliced isoforms of ATP5H, encoded by a gene that maps to human chromosome 17q25.1, are known. ATP5H is restricted to mitochondrial inner membrane.

ATP synthase subunit O (ATP5O) localizes to the mitochondria and catalyzes ATP synthesis. ATP5O is a component of the F-type ATPase found in the mitochondrial matrix. F-type ATPases are composed of a catalytic core and a membrane proton channel. ATP5O seems to be part of the connector connecting these two components and may be involved in transmission of conformational changes or proton conductance.

ATP5F1 is a mitochondrial ATP synthase subunit catalyzes ATP synthesis, using an electrochemical gradient of protons all through the inner membrane for the duration of the oxidative phosphorylation. ATP synthase is comprised of two linked multi-subunit complexes: the soluble catalytic core, F1, and the membrane-spanning component, Fo, including the proton channel. The catalytic segment of mitochondrial ATP synthase contains 9 subunits: 3 alpha, 3 beta, and one unit of gamma, delta, and epsilon. The proton route is known to have 9 subunits (a, b, c, d, e, f, g, F6 and 8).

F-ATPase delta (ATP5D) catalyzes ATP synthesis, employing an electrochemical gradient of protons across the inner membrane during oxidative phosphorylation. ATP synthase is composed of 2 linked multi-subunit complexes: F1-the soluble catalytic core and Fo- the membrane-spanning component, which comprise the proton channel. The catalytic portion of mitochondrial ATP synthase consists of five different subunits (alpha, beta, gamma, delta, and epsilon) assembled with a stoichiometry of 3 alphas, 3 betas, and a single representative of the other three. The proton channel consists of three main subunits-a, b, c. ATP5D is the delta subunit of the catalytic core.

ATP synthase subunit gamma, mitochondrial isoform L (liver) (ATP5C1) is a member of the ATPase gamma chain family. ATP5C1 catalyzes ATP synthesis by using an electrochemical gradient of protons across the inner membrane throughout oxidative phosphorylation. The catalytic portion of mitochondrial ATP synthase is comprised of 5 different subunits (alpha, beta, gamma, delta, and epsilon) gathered with a stoichiometry of 3 alpha, 3 beta, and a single representative of the other 3.

OXSM, a beta-ketoacyl synthetase, is essential for elongation of fatty acid chains in the mitochondria. Alternatively spliced transcript variants were found.

Adenylate kinases play a role in regulating the adenine nucleotide composition within a cell by catalyzing the reversible transfer of phosphate groups among adenine nucleotides. There are 3 types of adenylate kinase isozymes, AK1, AK2, and AK3 in vertebrates. Expression of these isozymes are tissue-specific and developmentally regulated. AK2 is localized in the mitochondrial intermembrane space and is involved in apoptosis. AK2 is mutated in individuals with reticular dysgenesis.

Citrate synthase also known as CS is a Krebs tricarboxylic acid cycle enzyme which catalyzes the synthesis of citrate from oxaloacetate and acetyl coenzyme A. CS is present in almost all cells capable of oxidative metabolism. CS is nuclear encoded and transported into the mitochondrial matrix, where the mature form is found. The diseases related to CS are: critical illness polyneuropathy and mitochondrial cardiomyopathy.

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.

ATPase Transporting, Lysosomal V1 Subunit F (ATP6V1F) is a component of vacuolar ATPase (V-ATPase); it is a multi-subunit enzyme, which mediates acidification of eukaryotic intracellular organelles. V-ATPase dependent organelle acidification is required for such intracellular processes as protein sorting, zymogen activation, receptor-mediated endocytosis, and synaptic vesicle proton gradient generation. V-ATPase is comprised of a cytosolic V1 domain and a transmembrane V0 domain. The V1 domain contains 3 A and 3 B subunits, 2 G subunits as well as the C, D, E, F, and H subunits. The V1 domain has the ATP catalytic site. The V0 domain consists of 5 different subunits: a, c, c', c', and d.

NT5M is a member of the 5'(3')-deoxyribonucleotidase family. NT5M localizes to the mitochondrial matrix. The NT5M enzyme dephosphorylates the 5'- and 2'(3')-phosphates of uracil and thymine deoxyribonucleotides. The NT5M gene is located on chromosome 17 p11.2 in the critical region deleted in the Smith-Magenis syndrome (SMS), a genetic disease of unidentified etiology.

Uroporphyrinogen III synthase (UROS) is an enzyme involved in the 4th step of porphyrin metabolism and in the conversion of hydroxymethyl bilane into uroporphyrinogen III. Defects in the UROS protein can cause molecular lesions which lead to the autosomal recessive Gunther disease, otherwise known as congenital erythropoietic porphyria (CEP).

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 this gene are the reason of inherited orotic aciduria disease.

MECR catalyzes the reduction of trans-2-enoyl-CoA to acyl-CoA with chain length from C6 to C16 in an NADPH dependent manner with preference to medium chain length substrate. MECR protein takes part in the mitochondrial synthesis of fatty acids.

L-threonine to glycine degradation consists of a two-step biochemical pathway which involvs the enzymes L-threonine dehydrogenase and 2-amino-3-ketobutyrate coenzyme A ligase. L-Threonine is initially converted into 2-amino-3-ketobutyrate by L-threonine dehydrogenase. Glycine C-Acetyltransferase (GCAT) is the 2nd enzyme in this pathway, which subsequently catalyzes the reaction between 2-amino-3-ketobutyrate and coenzyme A to form glycine and acetyl-CoA. The GCAT enzyme is regard as a class II pyridoxal-phosphate-dependent aminotransferase. GCAT is strongly expressed in the heart, brain, liver and pancreas. GCAT is also found in lung.

NADH dehydrogenase [ubiquinone] iron-sulfur protein 3 (NDUFS3) is a member of the complex I 30 kDa subunit family. NDUFS3 is one of the iron-sulfur protein (IP) components of mitochondrial NADH:ubiquinone oxidoreductase (complex I). This complex is the first enzyme complex in the electron transport chain of mitochondria. The iron-sulfur protein (IP) fraction of complex I consists of seven subunits. NDUFS3 gene mutations are linked with Leigh syndrome resulting from mitochondrial complex indefficiency.

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).

Mimitin (NDUFAF2) is a member of the complex I NDUFA12 subunit family.NADH dehydrogenase is an enzyme located in the inner mitochondrial membrane, which catalyzes the transfer of electrons from NADH to coenzyme Q (CoQ). NDUFAF2 is the "entry enzyme" of oxidative phosphorylation in the mitochondria. Mimitin protein functions as a molecular chaperone for mitochondrial complex I assembly.

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.

ECHS1 is part of the hydratase/isomerase superfamily. ECHS1 is localized in the mitochondrial matrix and Expressed in muscle, liver and fibroblasts, with low expression in kidney and spleen, ECHS1 exists as a homohexamer that takes part in the second phase of the mitochondrial fatty acid β-oxidation pathway.

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.

Polyribonucleotide nucleotidyltransferase 1, also known as PNPT1 is predominantly localized in the mitochondrial intermembrane space and is implicated in the import of RNA to mitochondria. Mutations in PNPT1 have been connected with combined oxidative phosphorylation deficiency-13 as well as autosomal recessive nonsyndromic deafness-70. Related pseudogenes have been found on chromosomes 3 & 7.

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.

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.