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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.

Alcohol dehydrogenase 1A (ADH1A) is a member of the alcohol dehydrogenase family. ADH1A has a key role in ethanol metabolism. ADH1A along with coenzyme NAD catalyzes the reversible conversion of organic alcohols to ketones or aldehydes. The physiologic function of ADH1A in the liver is the elimination of ethanol formed by microorganisms in the intestinal tract. ADH1A is monomorphic and predominant in fetal and infant livers, growing to be less active in gestation and only weakly active during adulthood.

Seryl-tRNA synthetase, cytoplasmic (SARS) is a member of the class-II aminoacyl-tRNA synthetase family. Aminoacyl-tRNA synthetases’ role is to catalyze the aminoacylation of tRNAs by their corresponding amino acids, as a result linking amino acids with tRNA-contained nucleotide triplets. The SARS enzyme catalyzes the attachment of serine to tRNA (Ser). SARS enzyme is probably able to aminoacylate tRNA (Sec) with serine, to form the misacylated tRNA L-seryl-tRNA (Sec), which will be then converted into selenocysteinyl-tRNA (Sec).

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.

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.

MAT2A is an important enzyme in cellular metabolism and catalyzes the formation of S-adenosylmethionine (SAMe) from L-methionine and ATP. MAT2A is expressed in extrahepatic tissues. In liver, MAT2A expression associates with growth, dedifferentiation, and cancer. NF-kappa B and AP-1 are necessary for basal MAT2A expression in HepG2 cells and mediate the increase in MAT2A expression in response to TNF-alpha. Up-regulation of MAT2A provides growth improvement and s-adenosylmethionine and methylthioadenosine thus can block mitogenic signaling in colon cancer cells. Lower expression of both MAT2A and MAT2beta and interfere with leptin signaling in liver cancer cells.

Acid phosphatase, prostate (ACPP) is a non-specific tyrosine phosphatase, which dephosphorylates a varied number of substrates under acidic conditions (pH 4-6) including alkyl, aryl, and acyl orthophosphate monoesters and phosphorylated proteins. ACPP has lipid phosphatase activity and inactivates lysophosphatidic acid in seminal plasma.

Mitochondrial Ribosomal Protein S23, also known as MRPS23 belongs to the mammalian mitochondrial ribosomal proteins which are encoded by nuclear genes and assist in proteinsynthesis inside the mitochondrion. Mitochondrial ribosomes consist of a small 28S subunit and a large 39S subunit. In addition, they have an estimated 75% protein to rRNA composition compared to prokaryotic ribosomes, where this ratio isreversed. An additional difference between mammalian mitoribosomes and prokaryotic ribosomes is that the lattercontain a 5S rRNA. Between different species, the proteins containing the mitoribosome differ very much in sequence, and occasionally in biochemical properties, which prevents easy recognition by sequence homology.

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.

PAPSS1 is a bifunctional enzyme with APS kinase and ATP sulfurylase activity. PAPSS1 facilitates two stages in the sulfate activation pathway, yielding 3'-phosphoadenylylsulfate (PAPS). Additionally, PAPSS1 takes part in the biosynthesis of sulfated L-selectin ligands in endothelial cells.

Ecto-ADP-Ribosyltransferase 4 or ART4 is typed as a glycosylphosphatidylinositol (GPI)-linked membrane protein which carries Dombrock blood group antigens. The development of this protein takes place at the highest levels in the fetal liver. the process of the ART4 development is regulated while the erythroid differentiation process occurs. ART4 is a is part of the Ribosyltransferase family.

NADH Dehydrogenase Flavoprotein 2 (NDUFV2) is a 24 kDa Core subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I) which is a part of the minimal assembly required for catalysisthe. NDUFV2 is aslo involved in electron transfer. Mutations in NDUFV2 are implicated in Parkinson's disease, bipolar disorder, schizophrenia, and have been discovered in one case of early onset hypertrophic cardiomyopathy and encephalopathy.

Porphobilinogen deaminase (HMBS) belongs to the hydroxymethylbilane synthase superfamily. HMBS is a cytoplasmic enzyme found in the heme synthesis pathway. HMBS is the 3rd enzyme of the heme biosynthetic pathway and catalyzes the head to tail condensation of 4 porphobilinogen molecules into the linear hydroxymethylbilane. HMBS gene mutations cause errors in pyrrole metabolism which in turn lead to the autosomal dominant disease acute intermittent porphyria.

Methionyl Aminopeptidase 1D (METAP1D) is a part of the peptidase M24A family. METAP1D which is overexpressed in colon cancer cell lines participates in tumorigenesis. METAP1D eliminates methionine from the N-terminus of nascent proteins.

Cytochrome C Oxidase Subunit Va (COX5A) is a member of the cytochrome c oxidase subunit 5A family. COX (Cytochrome C Oxidase), which is the terminal component of the mitochondrial respiratory chain, catalyzes the electron transfer from reduced Cytochrome C to oxygen. The COX component is a heteromeric complex comprised of three catalytic subunits encoded by mitochondrial genes and multiple structural subunits encoded by nuclear genes. The mitochondrially-encoded subunits serve in electron transfer, and the nuclear-encoded subunits act in the regulation and assembly of the complex. COX5A is the heme A-containing chain of Cytochrome C Oxidase,which is the terminal oxidase in mitochondrial electron transport.

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.

Enoyl-CoA Delta Isomerase 1 (ECI1) is a main mitochondrial enzyme which takes part in beta-oxidation of unsaturated fatty acids. ECI1 is a member of the hydratase/isomerase superfamily. ECI1 catalyzes the transformation of 3-cis and 3-trans-enoyl-CoA esters to the 2-trans-enoylCoA intermediates.

Mammalian mitochondrial ribosomal proteins are encoded by nuclear genes and aid in protein synthesis within the mitochondrion. Mitochondrial ribosomes (mitoribosomes) comprised of a small 28S subunit and a large 39S subunit. Among different species, the proteins comprising the mitoribosome vary greatly in sequence, and sometimes in biochemical properties, thus preventing simple recognition by sequence homology. Mitochondrial Ribosomal Protein L2 (MRPL2) is a 39S subunit protein which is a member of the EcoL2 ribosomal protein family.

MAT1A catalyzes a two-step reaction that involves the transfer of the adenosyl moiety of ATP to methionine to form S-adenosylmethionine and tripolyphosphate, which is subsequently cleaved to PPi and Pi. S-adenosylmethionine is the source of methyl groups for most biological methylations. MAT1A is found as a homotetramer (MAT I) or a homodimer (MAT III) whereas a third form, MAT II (gamma), is encoded by the MAT2A gene. Mutations in MAT1A gene are associated with methionine adenosyltransferase deficiency. MAT1A expression also correlates with a differentiated phenotype, whereas liver cells expressing MAT2A present a dedifferentiated phenotype and lowered AdoMet synthesis. Likewise, NFκB and TNFα cause a switch from MAT1A to MAT2A expression in human hepatocellular carcinoma (HCC), which facilitates cancer cell growth.

Phosphoribosyl Pyrophosphate Synthetase 2, also known as PRPS2 is a member of the ribose-phosphate pyrophosphokinase family. PRPS2 catalyzes the synthesis of 5-phosphoribosyl 1-pyrophosphate from ATP and D-ribose 5-phosphate.

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.

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.

Mitochondrial rRNA methyltransferase 1 homolog (MRM1) is a part of the RNA methyltransferase TrmH family. MRM1 methylates the ribose of guanosine G-2270 in the peptidyl transferase center of the mitochondrial large ribosomal RNA (21S).

MRPS25, a 28S subunit protein, is a member of the ribosomal protein S5P family. An equivalent pseudogene is located on chromosome 4.