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Ubiquitin-conjugating enzyme E2S (UBE2S) belongs to the ubiquitin-conjugating enzyme family. UBE2S is able to form a thiol ester linkage with ubiquitin in a ubiquitin activating enzyme-dependent manner, a typical property of ubiquitin carrier proteins. UBE2S catalyzes the covalent attachment of ubiquitin to other proteins. UBE2S acts as a crucial factor of the anaphase promoting complex/cyclosome (APC/C), which is a cell cycle-regulated ubiquitin ligase that controls progression through mitosis. UBE2S acts by purposely elongating 'Lys-11'-linked polyubiquitin chains initiated by the E2 enzyme UBE2C/UBCH10 on APC/C substrates, augmenting the degradation of APC/C substrates by the proteasome and promoting mitotic exit. UBE2S also acts by elongating ubiquitin chains initiated by the E2 enzyme UBE2D1/UBCH5 in vitro; it is nevertheless uncertain whether UBE2D1/UBCH5 acts as an E2 enzyme for the APC/C in vivo. UBE2S is also involved in ubiquitination and consequent degradation of VHL, resulting in an accumulation of HIF1A.

SCO2 protein is a member of the SCO1/2 family. SCO1 and SCO2 proteins are found on the inner membrane of the mitochondria and takes a vital part copper insertion or transport to the active site of cytochrome c oxidase (COX). Flaws in SCO2 are the reason for deadly infantile cardioencephalomyopathy with cytochrome c oxidase deficiency (FIC) which is characterized by hypertrophic cardiomyopathy, lactic acidosis, and gliosis. Heart and skeletal muscle display declines in cytochrome c oxidase (COX) activity, while liver and fibroblasts show mild COX deficiencies.

UBE2D2 belongs to the E2 ubiquitin-conjugating enzyme family. UBE2D2 takes part in the ubiquitination of the tumor-suppressor protein p53, which is induced by an E3 ubiquitin-protein ligase. UBE2D2 catalyzes ubiquitination of IkB-alpha in a SCFB-TRCP and phosphorylation dependent method.

Human Ubquitin-conjugating enzyme 7 (UbcH7) is a ubiquitin-conjugating enzyme (E2) mediating c-fos degradation, transcription factor NF-B maturation, and human papilloma virus-mediated p53 and Myc protein degradation, in vitro. The ubiquitin-conjugating enzymes (E2s) are essential components of the post-translational protein ubiquitination pathway, mediating the transfer of activated ubiquitin to substrate proteins. The human UBE2L1-UBE2L4 gene could potentially encode different isoforms of the UbcH7. UBE2L3 gene, located at chromosome 22q11.2, is the only identical family member with introns and encodes a polypeptide sequence identical to that of UbcH7.

Aldo-Keto Reductase Family 7 Member A3 or AKR7A3, is an enzyme, it is part of the detoxification of aldehydes and ketones process. AKR7A3 diminishes the dialdehyde protein-binding form of aflatoxin B1 to the non-binding AFB1 dialcohol. The enzyme takes partin protection of liver from toxic and carcinogenic effects of AFB1, a potent hepatocarcinogen.

DCXR catalyzes the NADPH-dependent reduction of numerous pentoses, tetroses, trioses, alpha-dicarbonyl molecules and L-xylulose. DCXR takes part in the uronate cycle of glucose metabolism. DCXR participates in the water absorption and cellular osmoregulation in the proximal renal tubules by producing xylitol, an osmolyte, thus preventing osmolytic stress from occurring in the renal tubules.

AKR1C3 is part of the aldo/keto reductase superfamily, which has at least 40 identified proteins. AKR1C3 catalyzes the conversion of aldehydes and ketones to their corresponding alcohols by utilizing NADH and/or NADPH as cofactors. AKR1C3 displays overlapping but distinct substrate specificity. AKR1C3 catalyzes the reduction of prostaglandin (PG) D2, PGH2 and phenanthrenequinone (PQ), and the oxidation of 9alpha,11beta-PGF2 to PGD2. AKR1C3 is involved in the pathogenesis of allergic diseases such as asthma. AKR1C3 controls cell growth and/or differentiation. AKR1C3 takes part in adrenal testosterone production. AKR1C3 expression is affected by metabolic disease, and its levels are considerably reduced in response to diet-induced weight loss and correlate with leptin levels.

CYP2E1, also known as Cytochrome P450 2E1 belongs to the cytochrome P450 mixed-function oxidase system which is involved in the metabolism of xenobiotics in the body. While CYP2E1 is implicated in the oxidative metabolism of small range substrates, commonly small polar molecules, there are many significant drug interactions which are mediated by CYP2E1.

Human Ubquitin Conjugating Enzyme 7 (UbcH7) is a class I enzyme which functions in the stress response and the control of transcription factors. The enzyme is ubiquitously expressed with high levels of expression seen in adult muscle. UbcH7 mediates the selective degradation of short-lived and abnormal proteins and is highly homologous to UbcH5. It has been demonstrated to participate in the ubiquitinylation of p53, c-Fos and NF-?B. UbcH7 is one of two E2s (UbcH5 being the other) with which HECT domain proteins interact with UbcH7 being able to efficiently substitute for UbcH5 in E6-AP-dependent ubiquitinylation.

TRXR is a ubiquitous enzyme which participates in various cellular processes such as cell growth, p53 activity, and protection against oxidation stress. The mammalian Thioredoxin reductase cleaves thioredoxins as well as non-disulfide substrates such as selenite, lipoic acids, lipid hydroperoxides, and hydrogen peroxidec.

PECR is the main enzyme for a projected peroxisomal chain elongation pathway and is primarily expressed in kidney and liver.

Aldo-keto reductase family 1 member C1 or AKR1C1 is an enzyme, part of the aldo/keto reductase family that holds over 40 familiar proteins. AKR1C1 promotes the conversion of ketones & aldehydes to their alcohol forms by using cofactors such as NADH & NADPH. AKR1C1 promotes the progesterone reduction to its inactive molecule form 20-alpha-hydroxy-progesterone.

UBE2D3 enzymes are human homologs of the yeast UBC4/5 family and play many important regulatory roles in inflammation and cancer. UbcH5a mediates the degradation of a myriad of short-lived regulatory proteins (such as p53 in the presence of E6/E6-AP or MDM2, c-Fos, I?B?, p105) and abnormal proteins. UBE2D3 has 88% and 89% sequence identity with UbcH5a and UbcH5b respectively.

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.

UBE2T is part of the E2 ubiquitin-conjugating enzyme family that participates in the protein degradation pathway. UBE2T catalyzes the ATP-dependent attachment of ubiquitin to target proteins, thus tagging them for subsequent destruction by the proteasome. UBE2T is an important factor of the Faconi anemia pathway of DNA damage repair and, upon self-inactivation, may negatively regulate the Faconi pathway.

Cytochrome b5 isoform 1 (CYB5A) is a member of the cytochrome b5 family. CYB5A is a membrane bound hemoprotein which functions as an electron carrier for several membrane bound oxygenases. Defects in the CYB5A gene are the cause of methemoglobinemia CYB5A-related (METHB-CYB5A), which is a form of methemoglobinemia (a hematologic disease characterized by the presence of excessive amounts of methemoglobin in blood cells, resulting in decreased oxygen carrying capacity of the blood, cyanosis and hypoxia).

PYCR1 is a universal housekeeping enzyme which catalyzes the NAD(P)H-dependent conversion of pyrroline-5-carboxylate to proline. PYCR1 enzyme also takes a physiologic part in the generation of NADP(+) in certain cell types. PYCR1 forms a homopolymer and localizes to the mitochondrion. Mutations in PYCR1 are the source of cutis laxa autosomal recessive type 2B (ARCL2B).

UBE2E1 belongs to the E2 ubiquitin-conjugating enzyme family. UBE2E1 accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins. UBE2E1 catalyzes the covalent attachment of ISG15 to other proteins. UBE2E1 mediates the selective degradation of short-lived and abnormal proteins. In vitro, UBE2E1 also catalyzes 'Lys-48'-linked polyubiquitination.

Biliverdin reductase A (BLVRA) is a member of the gfo/idh/mocA family. BLVRA is an enzyme that converts biliverdin to bilirubin, converting a double-bond between the second and third pyrrole ring into a single-bond. BLVRA reduces the gamma-methene bridge of the open tetrapyrrole, biliverdin IX alpha, to bilirubin with the simultaneous oxidation of a NADH or NADPH cofactor (Bilirubin + NAD(P)+ = biliverdin + NAD(P)H ).
BLVRA is a regulator for induction of activating transcription factor-2 and heme oxygenase-1. Furthermore, BLVRA enhances the role of HO-1 in cytoprotection and provides cytoprotection independent of heme degradation. In addition, Bilirubin while acting as a cytoprotective antioxidant is itself oxidized to biliverdin and subsequently recycled by biliverdin reductase back to bilirubin.

Ubiquitin carboxyl-terminal hydrolase isozyme L3 belongs to a gene family whose products hydrolyze small C-terminal adducts of ubiquitin to produce the ubiquitin monomer. UCHL3 takes part in the regulation of neuronal development and spermatogenesis and is associated to neurodegenerative diseases. UCHL3 has a 54% homology to UCHL1.

NQO1 belongs to the NAD(P)H dehydrogenase (quinone) family and encodes a cytoplasmic 2-electron reductase. NQO1 acts as an imperative part of cellular antioxidant defense by detoxifying quinines therefore preventing the formation of reactive oxygen species. It seems that NQO1 serves as a quinone reductase relating to conjugation reactions of hydroquinons involved in detoxification pathways in addition to biosynthetic processes such as the vitamin K-dependent gamma-carboxylation of glutamate residues in prothrombin synthesis. Altered NQO1 expression is seen in many tumors and also linked to Alzheimer’s disease. NQO1 gene mutations are linked to tardive dyskinesia which is an increased risk of hematotoxicity after exposure to benzene, and susceptibility to various forms of cancer.

Cytochrome c oxidase assembly factor 4 (COA4) is the last enzyme of the mitochondrial respiratory chain which needs a great number of accessory factors. COA4 is vital for oxidative phosphorylation and comprises multiple complexes including cytochrome c oxidase, assembled in macromolecular supercomplexes. COX4 is a protein-coding gene which defect in it causes an acute human encephalomyopathies.

Human Ubquitin Conjugating Enzyme 9 (Ubc9) is a member of the E2 family and is specific for the conjugation of SUMO to a variety of target proteins. SUMO conjugation to target proteins is mediated by a different, but analogous, pathway to ubiquitinylation. This E2 is unusual in that it interacts directly with protein substrates that are modified by sumolyation, and may play a role in substrate recognition. Ubc9 can mediate the conjugation of SUMO-1 to a variety of proteins including RanGAP1, I?B?, and PML without the requirement of an E3 ligase.