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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.

Guanosine monophosphate reductase (GMPR) catalyzes the irreversible NADPH-dependent deamination of GMP to IMP. GMPR acts in the conversion of nucleobase, nucleoside and nucleotide derivatives of G to A nucleotides, and in upholding the intracellular balance of A and G nucleotides. In addition, the GMPR protein functions in the re-utilization of free intracellular bases and purine nucleosides.

UPRT is a uracil phosphoribosyltransferase, that catalyzes the alteration of uracil and 5-phosphoribosyl-1-R-diphosphate to uridine monophosphate (UMP). This reaction is a significant part of nucleotide metabolism, specifically the pyrimidine salvage pathway. UPRT is restricted to the nucleus and cytoplasm and is a possible target for rational design of drugs to cure cancer and parasitic infections.

Galactose-1-Phosphate Uridylyltransferase (GALT) catalyzes the 2nd step of the “Leloir pathway” of galactose metabolism, specifically the conversion of UDP-glucose + galactose-1-phosphate to glucose-1-phosphate + UDP-galactose. The deficiency of the GALT enzyme results in typical galactosemia in humans and may be fatal in the newborn stage if lactose is not eliminated from the diet. Galactosemia pathophysiology has not been clearly defined.

Aldolase C Fructose-Bisphosphate (ALDOC) belongs to the class I fructose-bisphosphate aldolase family. ALDOC is a glycolytic enzyme which catalyzes the reversible aldol cleavage of fructose-1,6-biphosphate and fructose 1-phosphate to dihydroxyacetone phosphate and either glyceraldehyde-3-phosphate or glyceraldehydes respectively. ALDOC is expressed exclusively in the hippocampus and Purkinje cells of the brain.

FEN1 removes 5'' overhanging flaps in DNA repair and processes the 5'' ends of Okazaki fragments in lagging strand DNA synthesis. The interaction between FEN1 and AP endonuclease 1 during long-patch base excision repair provides coordinated loading of the proteins onto the substrate, therefore passing the substrate from one enzyme to another. FEN1 is part of the XPG/RAD2 endonuclease family and is one of ten proteins essential for cell-free DNA replication. DNA secondary structure can inhibit flap processing at certain trinucleotide repeats in a length-dependent manner by concealing the 5'' end of the flap that is necessary for both binding and cleavage by the protein encoded by this gene. Therefore, secondary structure can deter the protective function of this protein, leading to site-specific trinucleotide expansions.

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.

tRNA aspartic acid methyltransferase 1 (TRDMT1) is a member of the C5-methyltransferase family. TRDMT1 specifically methylates cytosine 38 in the anticodon loop of tRNA(Asp). TRDMT1 is a protein responsible for the methylation of aspartic acid transfer RNA, particularly at the cytosine-38 residue in the anticodon loop. In addition, the TRDMT1 enzyme has residual DNA-(cytosine-C5) methyltransferase activity. TRDMT1 is expressed ubiquitously; however it has a higher expression in the testis, ovary and thymus and at much lower levels in the spleen, prostate, colon, small intestine, and peripheral blood leukocytes. Though similar in sequence and structure to DNA cytosine methyltransferases, the TRDMT1 gene is distinctive and extremely conserved in its function between taxa.

GPI or Glucose-6-phosphate isomerase, is a protein, part of the multifunctional phosphoglucose isomerase family, which its members take part in energy pathways. GPI is a dimeric enzyme that enhances the isomerization of glucose-6-phosphate and fructose-6- phosphate (both reversible). In mammals, GPI acts as an angiogenic factor & tumor-secreted cytokine. The enzyme also acts as a neurotrophic factor for spinal & sensory neurons.

SAT-1 is a member the acetyltransferase family, and is a rate-limiting enzyme in the catabolic pathway of polyamine metabolism. SAT1 catalyzes the acetylation of spermidine and spermine, and is involved in the regulation of the intracellular concentration of polyamines and their transport out of cells. Therefore, SAT-1’s role is essential in polyamine homoeostasis, given that acetylated products are either excreted from the cell or oxidized by acetylpolyamine oxidase. Increased SAT1 activity causes variety of other effects which include pancreatic cells death, obstruction of regenerative tissue growth, behavioral changes, keratosis follicularis spinulosa decalvans (KFSD), and hair loss.
Defects in the SAT1 gene are linked to KFSD (keratosis follicularis spinulosa decalvans), which is a rare X-linked disorder affecting the skin and the eye. The KFSD affected men show thickening of the skin of the neck, ears, and extremities, particularly the palms and soles, loss of eyebrows, eyelashes and beard, thickening of the eyelids with blepharitis and ectropion, and corneal degeneration. Even though the majority of the affected families are compatible with an X-linked inheritance, KFSD are found to be clinically and genetically heterogeneous.

GDA is a member of the ATZ/TRZ family and is in charge for the hydrolytic deamination of guanine. GDA takes part in microtubule assembly. Multiple transcript variants encoding different isoforms have been found for GDA.

Phosphomannomutase 1 (PMM1) is an enzyme involved in the synthesis of the GDP-mannose and dolichol-phosphate-mannose required for a number of critical mannosyl transfer reactions. PMM1 catalyzes the conversion between D-mannose 6-phosphate and D-mannose 1-phosphate which is a substrate for GDP-mannose synthesis. GDP-mannose is used for the synthesis of dolichol-phosphate-mannose, which is crucial for N-linked glycosylation and accordingly the secretion of several glycoproteins as well as for the synthesis of glycosyl-phosphatidyl-inositol (GPI) anchored proteins. Additionally, PMM1 may be responsible for the degradation of glucose-1,6-bisphosphate in ischemic brain.

Adenosine deaminase-like protein (ADAL) is a putative nucleoside deaminase. ADAL catalyzes the hydrolytic deamination of adenosine or some similar substrate and has a role in purine metabolism.

TAF9 is a universal transcription factor which enables the preinitiation complex assembly by direct interactions with the TATA promoter element. TAF9 is a multisubunit complex consisting of a small TATA-binding polypeptide and other TBP-associated factors (TAFs) and performs as a channel for regulatory signals.

Haloacid dehalogenase-like hydrolase domain-containing protein 1A (HDHD1A) is a member of the adiponutrin family. HDHD1A is interesting because it is an X-linked gene that escapes X-inactivation. HDHD1A is particularly important in the perception of human X chromosome structural organization as well as the mechanism of X-inactivation.

DCTD is an allosteric enzyme that exists as a homohexamer and is part of the cytidine and deoxycytidylate deaminase protein family. DTCD uses zinc as a cofactor to catalyze the deamination of dCMP to dUMP, thus making the nucleotide substrate (dUMP) that is used by thymidylate synthase.

Malate dehydrogenase (EC1.1.1.37) is an enzyme in the citric acid cycle that catalyzes the conversion of malate into oxaloacetate (using NAD+) and vice versa (this is a reversible reaction). Malate dehydrogenase is not to be confused with malic enzyme, which catalyzes the conversion of pyruvate using NADPH.
Malate dehydrogenase is also involved in gluconeogenesis, the synthesis of glucose from smaller molecules. Pyruvate in the mitochondria is acted upon by pyruvate carboxylase to form oxaloacetate, a citric acid cycle intermediate. In order to get the oxaloacetate out of the mitochondria, malate dehydrogenase reduces it to malate, and it then traverses the inner mitochondrial membrane. Once in the cytosol, the malate is oxidized back to oxaloacetate by cytosolic malate dehydrogenase. Finally, phosphoenol-pyruvate carboxy kinase (PEPCK) converts oxaloacetate to phosphoenol pyruvate.

Tyrosyl-DNA phosphodiesterase 1 ( TDP1) is required for repairing stalled topoisomerase I-DNA complexes by catalyzing the hydrolysis of the phosphodiester bond between the tyrosine residue of topoisomerase I and the 3-prime phosphate of DNA. TDP1 also detach glycolate from single-stranded DNA having 3-prime phosphoglycolate, suggesting a role in repair of free-radical mediated DNA double-strand breaks.

N-acetylneuraminate lyase (NanA) is a member of a family of lyases, specifically the oxo-acid-lyases, which cleave carbon-carbon bonds. NanA catalyzes the cleavage of N-acetylneuraminic acid (sialic acid) to form pyruvate and N-acetyl-D-mannosamine. NanA is inhibited by reduction with NaBH4 in the presence of the substrate, which indicates that it belongs to the Schiff-base-forming Class I aldolases. NanA is strongly inhibited by Cu2+ ions, p-chloromercuribenzoate and N-bromosuccinimide, it is also inhibited competitively by the reaction product, pyruvate, and its structurally related compounds, dihydroxyacetone and DL-glyceraldehyde.

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.

Malate dehydrogenase (EC1.1.1.37) is an enzyme in the citric acid cycle that catalyzes the conversion of malate into oxaloacetate (using NAD+) and vice versa (this is a reversible reaction). Malate dehydrogenase is not to be confused with malic enzyme, which catalyzes the conversion of pyruvate using NADPH.
Malate dehydrogenase is also involved in gluconeogenesis, the synthesis of glucose from smaller molecules. Pyruvate in the mitochondria is acted upon by pyruvate carboxylase to form oxaloacetate, a citric acid cycle intermediate. In order to get the oxaloacetate out of the mitochondria, malate dehydrogenase reduces it to malate, and it then traverses the inner mitochondrial membrane. Once in the cytosol, the malate is oxidized back to oxaloacetate by cytosolic malate dehydrogenase. Finally, phosphoenol-pyruvate carboxy kinase (PEPCK) converts oxaloacetate to phosphoenol pyruvate.

DCTPP1, also known as dCTP pyrophosphatase 1, contains an epilepsy-associated repeat (EAR) domain that is predicted to participate in protein-protein interactions, most likely involved in ligand recognition. This protein functions to hydrolyze abnormal nucleotide triphosphates (NTPs) in cancer cells that, if unregulated, could be incorporated into nascent DNA or RNA.