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Chitodextrinase is a unique membrane-bound endoenzyme. The chitodextrinase enzyme cleaves soluble oligomers, but not chitin, to the di- and trisaccharides. Chitodextrinase is unable to solubilize chitin, but it can catalyze the hydrolysis of high to low molecular weight soluble chitin oligosaccharides.

Dihydrofolate reductase (DHFR) is an enzyme that reduces dihydrofolic acid to tetrahydrofolic acid, with NADPH as electron donor that can be converted to the kinds of tetrahydrofolate cofactors applied in 1-carbon transfer chemistry. DHFR converts dihydrofolate into tetrahydrofolate, which is a methyl group shuttle required for the de novo synthesis of purines, thymidylic acid, and specific amino acids. Even though the functional DHFR gene is mapped to chromosome 5, numerous intronless processed pseudogenes or dihydrofolate reductase-like genes are identified on separate chromosomes. DHFR deficiency is associated with megaloblastic anemia. DHFR knockdown plays a role in the anticancer activity of 2-hydroxyoleic acid. DHFR gene insertion/deletion polymorphism is linked to variation in serum and red blood cell folate concentrations in women.

Ubiquitin-conjugating enzyme E2 H (UBE2H) is a member of the ubiquitin-conjugating enzyme family. Protein modification with ubiquitin is a vital cellular apparatus for directing abnormal or short-lived proteins for degradation. Ubiquitination requires at least 3 classes of enzymes: ubiquitin-activating enzymes (E1s) ubiquitin-conjugating enzymes (E2s) and ubiquitin-protein ligases (E3s). UBE2H receives ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. UBE2H protein sequence is 100% identical to the mouse homolog and 98% identical to the frog and zebrafish homologs.

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.

Biotinidase also known BTD, belongs to the nitrilase superfamily, which contains 12 families of nitrilases, amidases, carbamylases, and N-acyltrasferases. BTD catalyzes the hydrolysis of biocytin, the product of biotin-dependent carboxylase degradation, to biotin and lysine. BTD has a vital regulatory part in chromatin/DNA function. Mutations in BTD protein lead to Biotinidase deficiency.

PPCDC is a member of the HFCD (homo oligomeric flavin containing Cys decarboxylase) superfamily which takes a part in the biosynthesis of coenzyme A (CoA) from pantothenate (Vitamin B). The biosynthesis of CoA from pantothenate needs several steps: the phosphorylation of pantothenate, the conversion of 4’-hosphopantothenate to 4''-phosphopantetheine, the adenylation by phosphopantetheine adenylyltransferase to form dephospho-CoA and the phosphorylation by dephospho-CoA kinase to form CoA. PPCDC is a key player in this pathway. PPCDC converts 4''-phosphopantothenate into 4''-phosphopantetheine.

NUDT1 is an enzyme that hydrolyzes oxidized purine nucleoside triphosphates, such as 8-oxo-dGTP, 8-oxo-dATP, 2-hydroxy-dATP, and 2-hydroxy rATP, to monophosphates, thereby preventing misincorporation of 8-oxo-dGTP into DNA thus preventing A:T to C:G transversions. NUDT1 is found mostly in the cytoplasm, with some in the mitochondria, suggesting that it is involved in the sanitization of nucleotide pools both for nuclear and mitochondrial genomes. Moreover, NUDT1 is expressed at much higher levels in proliferating cells than in resting cells. Misincorporation of oxidized nucleoside triphosphates into DNA/RNA during replication and transcription can cause mutations which may result in carcinogenesis or neurodegeneration.

Indoleamine 2,3-Dioxygenase 1 (IDO1) catalyzes the primary and rate-limiting stage in tryptophan catabolism to N-formyl-kynurenine. IDO1 affects on various tryptophan substrates including D-tryptophan, and serotonin and is expressed in dendritic cells, monocytes, and macrophages. IDO1 takes part in a range of pathophysiological processes like neuropathology, antimicrobial and antitumor defense, immunoregulation, and antioxidant activity. IDO1 regulates T-cell behavior by its pericellular catabolization of the necessary amino acid tryptophan.

GSTZ1 is part of the glutathione S-transferase super-family which encodes multifunctional enzymes vital in the detoxification of electrophilic molecules, including carcinogens, mutagens, and several therapeutic drugs, by conjugation with glutathione. GSTZ1 participates in the catabolism of phenylalanine and tyrosine. Thus defects in GSTZ1 cause harsh metabolic disorders including alkaptonuria, phenylketonuria and tyrosinaemia. GSTZ1 is a bifunctional protein which has minimal glutathione-conjugating activity with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole and maleylacetoacetate isomerase activity. GSTZ1 has low glutathione peroxidase activity with T-butyl and cumene hydroperoxides. GSTZ1 catalyzes the glutathione dependent oxygenation of dichloroacetic acid to glyoxylic acid.

Adenosine Deaminase (ADA), also recognized as ADAT2 is an enzyme that takes part in purine metabolism. ADAT2 is necessary for the breakdown of adenosine from food and for the turnover of nucleic acids in tissues. ADAT2 is involved in the deamination of adenosine-34 to inosine in numerous tRNAs. ADAT2 is part of the cytidine and deoxycytidylate deaminase protein family, ADAT2 employs zinc as a cofactor. ADAT2 is a 191 amino acid enzyme that exists as two isoforms formed by alternative splicing events.

Putative peptidyl-tRNA hydrolase PTRHD1 (PTRHD1) is a 140 amino acid protein, which is encoded by a gene located on human chromosome 2p23.3. Chromosome 2 is the second largest human chromosome; it consists of 237 million bases, encodes over 1,400 genes and makes up approximately 8% of the human genome. Several genetic diseases are linked to genes on chromosome 2.

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.

Glutamate Decarboxylase 1 Isoform-1, also known as GAD1 iso1 belongs to the group II decarboxylase family. GAD1 iso1 encodes one of several forms of glutamic acid decarboxylase, and is identified as a major autoantigen in insulin-dependent diabetes. GAD1 iso1 is in charge for catalyzing the production of gamma-aminobutyric acid from L-glutamic acid. In addition, a pathogenic function for GAD1 iso1 has been shown in the human pancreas while it has been identified as an autoantigen & an autoreactive T cell target in insulin-dependent diabetes. GAD1 iso1 play a role in the stiff man syndrome. It has been shown that deficiency in this enzyme has led to pyridoxine dependency with seizures.

CBR1 is a NADPH-dependent, monomeric, and cytosolic enzyme which is related to a family of short-chain dehydrogenases/reductases. CBR1 protein (277 a.a.) is broadly spread in human tissues such as liver, epidermis, stomach, small intestine, kidney, neuronal cells, and smooth muscle fiber. CBR1 metabolizes numerous toxic environmental quinones and pharmacological relevant substrates such as the anticancer drug, doxorubicin. The best substrates of CBR1 are quinones, including ubiquinone-1 and tocophrolquinone (vitamin E).

NUDT2 belongs to the MutT family of nucleotide pyrophosphatases, a subset of the larger NUDIX hydrolase family. NUDT2 conserves homeostasis by using water to cleave the metabolite NUDT symmetrically back into its original ATP and AMP molecules. In addition, NUDT2 is active towards other adenosine and diadenosine polyphosphates with four or more phosphate groups, however, not towards diadenosine triphosphate. NUDT2 has a role in heat shock and metabolic stress by regulating intracellular dinucleoside polyphosphate concentrations.

Hydroxyacid Oxidase 1 (HAO1) is a part of the superfamily of the alpha hydroxy acid oxidases (HAO) enzymes. HAO1 catalyses the FMN mediated oxidation of glycolate to glyoxylate and glyoxylate to oxalate by reducing oxygen to hydrogen peroxide. HAO1 is expressed mainly in the liver and pancreas and is most active on twocarbon substrates such as glycolate. HAO1 isthe main cause of hyperoxaluria, a disorder in which large deposits of calcium oxalate form kidney stones.

Leukotriene A-4 hydrolase (LTA4H) is a bifunctional enzyme that converts leukotriene A4 to leukotriene B4 and functions as an aminopeptidase. The LTA4H enzyme is a member of the family of hydrolases, specifically those acting on ether bonds (ether hydrolases). LTA4H participates in arachidonic acid metabolism.

PRDX4 is an antioxidant enzyme that is part of the peroxiredoxin family. PRDX4 is localized to the cytoplasm. PRDX4 reduces hydrogen peroxide and alkyl hydroperoxides to water and alcohol with the use of reducing equivalents derived from thiol-containing donor molecules. PRDX4 has a regulatory part in the activation of the transcription factor NF-kappaB. PRDX4 participates in redox regulation of the cell. PRDX4 regulates the activation of NF-kappa-B in the cytosol by a modulation of I-kappa-B-alpha phosphorylation.

GOT2 is a pyridoxal phosphate-dependent enzyme which is found in cytoplasmic and inner-membrane mitochondrial forms, GOT1 and GOT2. GOT2 is invloved in amino acid metabolism and the urea and tricarboxylic acid cycles. The 2 enzymes are homodimeric and demonstrate close homology.

N-acylneuraminate-9-phosphatase (NANP) belongs to the haloacid dehalogenase (HAD) family and is responsible for dephosphorylating N-acylneuraminate 9-phosphate to form N-acylneuraminate (N-acylneuraminate 9-phosphate + H2O = N-acylneuraminate + phosphate). The catalytic activity of NANP is relies on the presence of magnesium and is inhibited by vanadate and calcium, which is typical of the HAD phosphatase family.

Formylglutathione hydrolase (Esterase D) is a member of the esterase D family. Esterase D is a serine hydrolase involved in the detoxification of formaldehyde. Esterase D is active toward various substrates including O-acetylated sialic acids, and it may possibly be involved in the recycling of sialic acids. Esterase D is used as a genetic marker for retinoblastoma and Wilson's disease.

GOT1 is a pyridoxal phosphate-dependent enzyme which exists in cytoplasmic and mitochondrial forms, GOT1 and GOT2, which participate in amino acid metabolism and the urea and tricarboxylic acid cycles. Both enzymes are homodimeric and show close homology.

Acireductone dioxygenase 1 (ADI1) is a part of the acireductone dioxygenase family of metal-binding enzymes, which are involved in methionine salvage. ADI1 regulates mRNA processing in the nucleus, and carries out different functions depending on its localization. Related pseudogenes have been defined on chromosomes 8 and 20. ADI1 down-regulates cell migration arbitrated by MMP14.

Thioredoxin reductase (TrxR/NTR), an enzyme belonging to the flavoprotein family of pyridine nucleotide-disulfide oxidoreductases. Thioredoxin reductase (TrxR), a component of the thioredoxin system, including thioredoxin (Trx) and NADPH, catalyzes the transfer of electrons from NADPH to Trx, acts as a reductant of disulfide-containing proteins and participates in the defense system against oxidative stresses.