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NQO2 is a flavoprotein that catalyzes the 2-electron reduction of diverse quinones, redox dyes, and the vitamin K menadione. NQO2 mainly uses dihydronicotinamide riboside (NRH) as the electron donor. NQO2 catalyzes the metabolic detoxification of quinones and their derivatives to hydroquinones. This detoxification process protects cells against quinone-induced oxidative stress, cytotoxicity and mutagenicity.

Cytidine deaminase (CDA) is an enzyme that scavenges exogenous and endogenous cytidine and 2'-deoxycytidine for UMP synthesis. CDA is one of several deaminases responsible for maintaining the cellular pyrimidine pool. CDA also catalyzes the deamination of chemotherapeutic cytosine nucleoside analogs such as Ara-C and 5-azacytidine, which results in the loss of their cytotoxic and antitumor function. CDA can form homotetramers and is generally expressed in granulocytes. Mutations in the CDA gene are linked to decreased sensitivity to the cytosine nucleoside analogue cytosine arabinoside used in the treatment of certain childhood leukemias.

GNMT is an enzyme that catalyzes the conversion of S-adenosyl-L-methionine with glycine to S-adenosyl-L-homocysteine. GNMT is located in the cytoplasm and acts as a homotetramer. Defects in the GNMT gene causes of GNMT deficiency (hypermethioninemia). GNMT affects DNA methylation by regulating the ratio of S-adenosylmethionine to S-adenosylhomocystine and is involved in the detoxification pathway in liver cells. GNMT expression is diminished in human hepatocellular carcinoma (HCC). GNMT catalyzes the methylation of glycine by using s- adenosylmethionine (adomet) to form n-methylglycine with the concomitant production of s-adenosylhomocysteine (adohcy). GNMT plays an essential role in the regulation of tissue concentration of adomet and of metabolism of methionine.

Angiotensin converting enzyme 2 or ACE-2 is an enzyme that is located in the cell membranes in different organs such as kidney, intestines, lungs, heart & arteries. ACE2 acts as an entry receptor of SARS coronaviruses & SARS-CoV-2.The coronavirus spike (S) glycoprotein is a class I viral fusion antigen bound to the external envelope of the virion that has a role in a crucial part in viral infection by identifying host cell receptors and starting fusion of the viral and cellular membranes. Couple of main domains in coronavirus S1 have been identified, the N-terminal domain and C-terminal domain. One or the other and/or both S1 domains acts as a receptor-binding domain. SARS-CoV + MERS-CoV equally use C-domain to attach their receptors.ACE2 is a type I transmembrane antigen with an extracellular N-terminal domain having the catalytic site and an intracellular C-terminal tail. ACE2 has a signal peptide, a transmembrane domain & a single metalloproteinase active site holds an HEXXH zinc-binding domain. ACE-2 takes part as a mono-carboxypeptidase which degrades Ang I to produce the nonapeptide Ang 1–9 and Ang II to create the heptapeptide Ang 1–7.

Antioxidant enzyme Glutathione S- Transferase (GST) is thought to do the primary cellular defense mechanism against reactive oxygen species. GST reduces lipid hydroperoxides through its Se-independent glutathione peroxidase activity. The enzyme also detoxifies lipid peroxidation end products such as 4-hydroxynonenal (4-HNE).
The soluble GST is a 26 kDa protein which occurs as a dimer in all aerobic organisms. Each monomer has two domains, one that binds GSH and is an /-structure similar to thioredoxin and the other, all helical, that binds the hydrophobic substrate. The GST -fusion protein expression system is a widely used recombinant protein expression system that allows a peptide or a regulatory protein domain to be expressed as a fusion to the C-terminus of Schistosoma japonicum GST. Fusion proteins also possess GST -enzymatic activity and can undergo dimerization similar to in vivo. The fusion protein can be purified via GST -affinity column chromatography. In most cases, the desired peptides or domains are removed from GST by applying a specific protease that recognizes and cleaves the linker between the protein domain and GST. The technique has been widely used to generate different kinds of proteins for crystallization, molecular immunology studies, the production of vaccines and studies involving protein-protein and protein-DNA interactions.

MPI is a member of the mannose-6-phosphate isomerase type 1 family. Although MPI is expressed in all tissues, it can be found more abundantly in heart, brain and skeletal muscle. Localized to the cytoplasm, MPI exploits zinc as a cofactor and catalyzes the interconversion of fructose-6-phosphate and mannose-6-phosphate. Mutations in the MPI gene are the cause of carbohydrate-deficient glycoprotein syndrome, type Ib.

Cystathionine gamma-lyase or cystathionase (CTH) is a member of the trans-sulfuration enzymes family. CTH is an enzyme which breaks down cystathionine into cysteine and alpha-ketobutyrate. The CTH catalyzes the last step in the transsulfuration pathway from methionine to cysteine. Glutathione synthesis in the liver is dependent upon the availability of cysteine. Mutations in the CTH gene cause cystathioninuria.

SUMF1 is a member of the SUMF family. SUMF1 catalyzes the hydrolysis of sulfate esters by oxidizing a cysteine residue in the substrate sulfatase to an active site 3-oxoalanine residue called C-alpha-formylglycine. Alterations in this gene result in multiple sulfatase deficiency which is a lysosomal storage disorder.

Dopa decarboxylase is a homodimeric, pyridoxal phosphate dependent enzyme.
Dopa decarboxylase is involved in 2 metabolic pathways, synthesizing 2 significant neurotransmitters the take part in numerous clinical disorders, including Parkinson’s disease. Dopa decarboxylase is located in different areas of the brain and is mostly found in basal ganglia. Dopa decarboxylase catalyzes the decarboxylation of L-3,4-dihydroxyphenylalanine (DOPA) to dopa, L-5-hydroxytryptophan to serotonin and L-tryptophan to tryptamine. Defects in Dopa decarboxylase leads to aromatic L-amino-acid decarboxylase deficiency (AADCD). AADCD deficiency is an inborn error in neurotransmitter metabolism that causes combined serotonin and catecholamine deficiency.

Glucose-6-phosphate isomerase (GPI) is a part of the GPI family whose members encode multifunctional phosphoglucose isomerase proteins involved in energy pathways. GPI is a dimeric enzyme which catalyzes the reversible isomerization of glucose-6-phosphate and fructose-6-phosphate. Mammalian GPI also functions as a tumor-secreted cytokine and an angiogenic factor (AMF) which stimulates endothelial cell motility. In addition, GPI is a neurotrophic factor (Neuroleukin) for spinal and sensory neurons. GPI performs in different capacities inside and outside the cell. In the cytoplasm, GPI is involved in glycolysis and gluconeogenesis, while outside the cell it acts as a neurotrophic factor for spinal and sensory neurons.
Defects in the GPI gene cause the nonspherocytic hemolytic anemia and a severe enzyme deficiency can be linked to hydrops fetalis, immediate neonatal death and neurological impairment.

Aminoacyl-tRNA synthetases are a class of enzymes that charge tRNAs with their cognate amino acids. The protein encoded by this gene is a cytoplasmic enzyme which belongs to the class II family of aminoacyl-tRNA synthetases. The enzyme is responsible for the synthesis of histidyl-transfer RNA, which is essential for the incorporation of histidine into proteins. The gene is located in a head-to-head orientation with HARSL on chromosome five, where the homologous genes share a bidirectional promoter. The gene product is a frequent target of autoantibodies in the human autoimmune disease polymyositis/dermatomyositis.

Napsin A Aspartic Peptidase, also known as NAPSA is a member of the peptidase A1 family. NAPSA is involved in the processing of pneumocyte surfactant precursors. Furthermore the activation peptides of aspartic proteinases take part as inhibitors of the active site. These peptide segments/pro-parts are considered essential for correct folding, targeting, as well as control of the activation of aspartic proteinase zymogens. The pronapsin A gene is expressed mostly in lung and kidney. In addition, NAPSA translation product is expected to be a fully functional, glycosylated aspartic proteinase precursor which contains an RGD motif as well as an additional 18 residues at its C-terminus.

Glutathione peroxidase 3 (GPX3) is a member of the glutathione peroxidase family, which acts in the detoxification of hydrogen peroxide. GPX3 shields cells and enzymes from oxidative damage, by catalyzing the reduction of hydrogen peroxide, lipid peroxides and organic hydroperoxide, by glutathione. The GPX3 protein is one of only a few proteins known in higher vertebrates to contain selenocysteine, which occurs at the active site of glutathione peroxidase and is coded by the nonsense (stop) codon TGA.

MGMT is an enzyme that repairs O-6-methylguanine, a mutagenic DNA base damaged by endogenous and environmental alkylating agents and takes part in the cellular defense against the biological effects of O-6-methylguanine in DNA. MGMT repairs alkylated guanine in DNA by stoichiometrically transferring the alkyl group at the O-6 position to a cysteine residue in the enzyme. abnormal MGMT expression correlates with the prognosis in human solid cancers. MGMT decrease of expression is correlated with methylation. The human MGMT is a negative regulator of estrogen receptor-mediated transcription upon alkylation DNA damage. MGMT promoter hypermethylation plays an important role in the early steps of colorectal carcinogenesis. Abnormal promoter hypermethylation of MGMT gene is associated with oral squamous cell carcinomas.

NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 5 (NDUFA5) is a member of the complex I NDUFA5 subunit family. The human NDUFA5 gene codes for the B13 subunit of complex I of the respiratory chain that transfers electrons from NADH to ubiquinone. The NDUFA5 protein localizes to the inner mitochondrial membrane as part of the seven component-containing, water soluble 'iron-sulfur protein' (IP) fraction of complex I, even though its exact role is undetermined.

GLUL catalyzes the synthesis of glutamine from glutamate and ammonia. Glutamine is a major source of energy and that takes part in cell proliferation, inhibition of apoptosis, and cell signaling. GLUL is expressed during early fetal stages, and has a role in maintaining body pH by removing ammonia from circulation. Mutations in GLUL gene are related with congenital glutamine deficiency.

NMNAT1 enzyme is vital for NAD biosynthesis, catalyzing the condensation of nicotinamide mononucleotide (NMN) or nicotinic acid mononucleotide (NaMN) with the AMP moiety of ATP to form NAD or NaAD. NMNAT1 is widely expressed with high levels in skeletal muscle, heart, liver and kidney. This protein appears to have the ability to protect against axonal degeneration following mechanical or toxic insults.

UNG is a member of the Uracil-DNA glycosylase family. One of his functions is to prevent mutagenesis by eliminating uracil from DNAmolecules by cleaving the N-glycosylic bond and initiating the base-excision repair (BER) pathway. Uracil basesare formed as a result of cytosine deamination or misincorporation of dUMP residues. After a mutation is formed, the mutagenicthreat of uracil propagates through any subsequent DNA replication steps. Among the diseases associated with UNG are: congenital rubella, and immunodeficiency with hyper igm type 4.

ALDH5A1 is a mitochondrial NAD(+)-dependent succinic semialdehyde dehydrogenase, which is a member of the aldehyde dehydrogenase family of proteins. The ALDH5A1 protein functions as a mediator to the NADP+-dependent oxidation of aldehydes into acids and has an imperative role in the detoxification of alcohol-derived acetaldehyde, as well as in lipid peroxidation and in the metabolism of corticosteroids, biogenic amines and neurotransmitters. ALDH5A1 is expressed in various tissues, including the liver, heart, lung, brain, kidney and placenta. Deficiency in the ALDH5A1 enzyme, known as 4-hydroxybutyricaciduria, is a rare inborn error in the metabolism of the neurotransmitter 4-aminobutyric acid (GABA). In response to this defect, physiologic fluids from patients accumulate GHB, which is a compound with numerous neuromodulatory properties.

Carboxyl ester lipase also known as CEL, formely called cholesterol esterase or bile salt-stimulated lipase, is an enzyme with lipolytic capablity of hydrolyzing cholesteryl esters, tri-, di-, and mono- phospholipids, acylglycerol, ceramide and lysophospholipids. The carboxyl terminus of the enzyme controls enzymatic activity by creating hydrogen bonds with the surface loop to partlyshield the active site. The active catalytic site triad of serine-histidine-aspartate is centrally located in the enzyme structure and is partly covered by a surface loop. Bile salt binding to the loop domain set free the active site for accessibility by water-insoluble substrates. CEL is produced mainly in the pancreas and lactating mammary gland, thus the protein is also expressed in liver, macrophages, and in the vessel wall.

Glycogen phosphorylase (PYGL) converts from inactive phosphorylase B to active phosphorylase A by phosphorylation of serine residue 15. Activity of the PYGL enzyme is further regulated by numerous allosteric effectors and hormonal controls. The liver isozyme supplies the glycemic demands of the body in general whereas the brain and muscle isozymes supply just those tissues.

Serratia marcescens secretes an endonuclease that has exceptionally high specific activity to the medium that surrounds it. The Benzonase Nuclease is mainly used for elimination of nucleic acid contamination from purified proteins, downstream processing, reduction of viscosity etc. Nucleic acid contaminants are caused by nuclease released to the medium. The DNA is being destroyed by the release of the S. marcescens nuclease and it acts as the killer gene for the auto destruction of microorganisms.

DBH catalyzes the chemical reaction. DBH is an oxidoreductase which belongs to the copper type II, ascorbate-dependent monooxygenase family, in particular those performing on paired donors, with O2 as oxidant and incorporation or reduction of oxygen. The oxygen incorporated can not be derived from O2 with reduced ascorbate as one donor, as well as incorporation of one ato of oxygen into the other donor.