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Caspase 3 Apoptosis-Related Cysteine Peptidase (CASP3) belongs to the cysteine-aspartic acid protease (caspase) family. Sequential activation of caspases plays a key role in the execution-phase of cell apoptosis. Caspases exist as inactive proenzymes which undergo proteolytic processing at conserved aspartic residues to generate 2 subunits, large and small, that dimerize to create the active enzyme. CASP3 protein cleaves and activates caspases 6, 7 and 9, and the protein itself is processed by caspases 8, 9 and 10. CASP3 is the leading caspase involved in the cleavage of amyloid-beta 4A precursor protein, which is linked with neuronal death in Alzheimer's disease. In addition, CASP3 is involved in the cleavage of huntingtin. CASP3 also cleaves and activates sterol regulatory element binding proteins (SREBPs) between the basic helix-loop-helix leucine zipper domain and the membrane attachment domain. CASP3 initiates cell adhesion in sympathetic neurons through RET cleavage.

NEDD8 is part of the ubiquitin family. Human NEDD8 shares 60% amino acid sequence homology to ubiquitin. The NEDD8 system is essential for the regulation of protein degradation pathways involved in cell cycle progression, morphogenesis and tumorigenesis. NEDD8 is involved in cell cycle control and embryogenesis. Covalent attachment to its substrates requires prior activation by the E-1 complex UbE1c- appbp1 and linkage to the E-2 enzyme UbE2m. Attachment of NEDD8 to cullins activates their associated E-3 ubiquitin ligase activity, and thus promotes polyubiquitination and proteasomal degradation of cyclins and other regulatory proteins.

PSMF1 is a protein which hinders the activation of the proteasome by the 11S and 19S regulators. The 26S proteasome is a multicatalytic proteinase complex with an extremely ordered structure composed of 2 complexes, a 20S core and a 19S regulator. The 20S core is comprised of 4 rings of 28 non-identical subunits; 2 rings are composed of 7 alpha subunits and 2 rings are composed of 7 beta subunits.

G/U mismatch-specific DNA glycosylase (mug) is a part of the TDG/mug DNA glycosylase family. Mug is necessary for DNA damage lesion repair in stationary-phase cells. Mug protein removes three N4-ethenocytosine and takes away s the uracil base from mismatches in the order of U:G>U:A. The enzyme Uracil-N-Glycosylase removes uracil from the DNA leaving an AP position. Mug is also able to hydrolyzing the carbon-nitrogen bond among the sugar-phosphate backbone of the DNA and the mispaired base. The complementary strand guanine plays a role in substrate recognition.

Thymidine Kinase 1 (TK1) is a phosphotransferase (a kinase): 2'-deoxythymidine kinase, ATP-thymidine 5'-phosphotransferase. TK1 is present in 2 forms in mammalian cells, TK1 and TK2. Thymidine kinases hold a main function in the synthesis of DNA and thus in cell division, as they are part of the distinctive reaction chain to introduce deoxythymidine (present in the body fluids as a result of degradation of DNA from food and from dead cells) into the DNA. Thymidine kinase is necessary for the action of many antiviral drugs. Thymidine kinase is used to select hybridoma cell lines in production of monoclonal antibodies.

UCK2 is a member of the uridinekinase family. UCK2 catalyzes the phosphorylation of uridine monophosphate to uridine diphosphate and cytidine monophosphate. UCK2 has a part in the production of pyrimidine nucleoside triphosphates essential for RNA and DNA synthesis. Furthermore, an allele of this gene is an important player in mediating nonhumoral immunity to Hemophilus influenzae type B.

ABHD14B is a member of the AB hydrolase superfamily. ABHD14B has an alpha/beta hydrolase fold - a catalytic domain found in a large number of enzymes. In molecular biology, the alpha/beta hydrolase fold is common to a number of hydrolytic enzymes of broad differing phylogenetic source and catalytic function. The Ab hydrolase domain containing gene subfamily includes 15 mostly uncharacterized members. ABHD14B has hydrolase activity with p-nitrophenyl butyrate (in vitro) and is able to activate transcription.

SULT2B1 catalyzes the sulfate conjugation of numerous hormones, neurotransmitters, drugs and xenobiotic compounds. Sulfonation enhances the water solubility of molecules, and therefore their renal excretion, however it can also result in bioactivation to form active metabolites. SULT2B1b is localized in the cytosol and nuclei of human cells. SULT2B1b is selective for the sulfation of 3beta-hydroxysteroids such as dehydroepiandrosterone and pregnenolone, and participates in cholesterol sulfation in human skin.

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.

COAA is a member of the prokaryotic pantothenate kinase family and it is the first enzyme in the Coenzyme A biosynthetic pathway. COAA phosphorylates pantothenate (vitamin B5) to form 4'-phosphopantothenate. The key factor controlling the intracellular CoA concentration is the regulation of COAA activity by feedback inhibition.

Cytosolic and membrane-bound types of GST are encoded by 2 different supergene families. There are 8 classes of the soluble cytoplasmic mammalian GST: alpha, kappa, mu, omega, pi, sigma, theta and zeta. The mu class of enzymes functions in the detoxification of electrophilic compounds, including carcinogens, therapeutic drugs, environmental toxins and products of oxidative stress, by conjugation with glutathione. The genes encoding the mu class of enzymes are arranged in a gene cluster on chromosome 1p13.3 and aare highly polymorphic. These genetic differences can change an individual's resistance to carcinogens and toxins as well as affect the toxicity and efficacy of certain drugs. Null mutations of this class mu gene have been linked with the rise in a number of cancers.

PHPT1 is a member of the Janus protein familyand is 125 amino acid long. PHPT1 appears as a monomer in the cytoplasm and is an EDTA-insensitive phosphohistidine phosphatase. Overexpression of PHPT1 resolts in specific phosphohistidine phosphatase activity towards phosphopeptide I, with no activity detected towards phosphotyrosine, phosphothreonine and phosphoserine peptides.

Cell division protein kinase 5 (CDK5) belongs to the cyclin-dependent kinase family. CDK5 is essential for appropriate development of the brain and in order to be activated CDK5 must link to CDK5R1 or CDK5R2. CDK5 doesn't need phosphorylation on the T loop so that binding with the activator is enough to activate the kinase. CDK5 is engaged in the processes of neuronal maturation and migration, phosphorylating the central intracellular adaptor of the reeling signaling chain.

TPMT, thiopurine S-methyltransferase, is a cytosolic enzyme that metabolizes thiopurine drugs via S-adenosyl-L-methionine as the S-methyl donor and S-adenosyl-L-homocysteine as a byproduct. TPMT activity exhibits autosomal codominant genetic polymorphism, and patients inheriting TPMT-deficiency are at high risk of potentially fatal hematopoietic toxicity.

Avidin is a tetrameric protein of 4 identical subunits (homotetramer) which can bind to biotin with a high degree of affinity and specificity. The estimated molecular weight of Avidin in its tetrameric form is between 66-69 kDa. Avidin is produced in the oviducts of birds, reptiles and amphibians and is subsequently deposited in the whites of their eggs. In the chicken egg white, avidin makes up roughly 0.05% of total protein (approximately 1.8 mg per egg). 10% of Avidin’s molecular weight is ascribed to carbohydrate content which is composed of 4-5 mannose and 3 N-acetylglucosamine residues. Avidin has at least three distinctive oligosaccharide structural type which are similar in structure and composition. The dissociation constant (KD) of avidin is approximately 10-15M, making it one of the strongest known non-covalent bonds.

Histone deacetylase 8 (HDAC8) is a member of the class 1 of the histone deacetylase/acuc/apha family. HDAC8 is biologically involved in skull morphogenesis and metabolic control of the ERR-alpha/PGC1-alpha transcriptional complex. Histones play a key role in transcriptional regulation, cell cycle progression, and developmental events. Histone acetylation/deacetylation modifies chromosome structure and affects transcription factor access to DNA.

Matrix metalloproteinases are a family of zinc and calcium-dependent endopeptidases that break down extracellular matrix proteins. The MMP9 is secreted as a 92kDa zymogen. Cleavage of ProMMP-9 results in the active enzyme, having a molecular weight of approximately 82kDa. MMP9 is composed of the following domains: a gelatin-binding domain consisting of three fibronectin type II units, a catalytic domain containing the zinc-binding site, a proline-rich type V collagen-homologous domain and a hemopexin-like domain. MMP9 is produced by the several cell types: monocytes, macrophages, neutrophils, keratinocytes, fibroblasts, osteoclasts and endothelial cells. MMP9 is involved in inflammatory responses, tissue remodeling, wound healing, tumor growth and metastasis. MMP9 may also play an important part in local proteolysis of the extracellular matrix and in leukocyte migration, as well as in bone osteoclastic resorption. MMP9 cleaves type IV and type V collagens into large C-terminal three quarter fragments and shorter N-terminal one quarter fragments. MMP9 can also degrade fibronectin but not laminin or Pz-peptide.
MMP9 defects may be a cause of susceptibility to intervertebral disc disease (IDD), also known as lumbar disk herniation (LDH).

Carbohydrate Sulfotransferase 5 (CHST5) is a Golgi-embedded enzyme that is found in B cells, T cells and intestinal epithelium and is also mediates sulfation of keratan in cornea. CHST5 is a sulfotransferase that utilizes 3'-phospho-5'-adenylyl sulfate (PAPS) as sulfonate donor to catalyze the transfer of sulfate to position 6 of non-reducing N-acetylglucosamine residues of keratan. CHST5 works on the non-reducing terminal GlcNAc of short andlong carbohydrate substrates that have poly-N-acetyllactosamine structures.

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.

Lysyl-tRNA synthetase (KARS) is a member of the class-II aminoacyl-tRNA synthetase family. KARS exists as both mitochondrial and cytoplasmic isoforms produced by alternative splicing, and believed to have a role in autoimmune diseases, such as polymyositis or dermatomyositis. The KARS protein functions to catalyze the aminoacylation of tRNAs by their corresponding amino acids, so linking amino acids with tRNA-contained nucleotide triplets.

PLA2G7 is a secreted enzyme which catalyzes the degradation of platelet-activating factor to biologically inactive products. The PLA2G7 enzyme is produced by inflammatory cells and hydrolyzes oxidised phospholipids in LDL. In the blood, PLA2G7 goes mainly with LDL and less than 20% is coupled with HDL.
PLA2G7 is implicated in the development of atherosclerosis and is also a marker for cardiac disease. PLA2G7 might have a major physiologic effect in the presence of inflammatory bodily responses.
PLA2G7 alters the action of PAF (platelet-activating factor) by hydrolyzing the sn-2 ester bond to yield the biologically inactive lyso-PAF. PLA2G7 has specificity for substrates with a short residue at the sn-2 position. PLA2G7 is inactive against long-chain phospholipids.
PLA2G7 gene defects are the source of platelet-activating factor acetylhydrolase deficiency, which is a trait that is present in 27% of the Japanese population.

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.

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.