Glucuronosyltransferase

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Glucuronosyltransferase
Identifiers
EC number 2.4.1.17
CAS number 9030-08-4
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO
UDP-glucuronosyl and UDP-glucosyl transferase
PDB 1rrv EBI.jpg
Structure of TDP-vancosaminyltransferase GtfD as a complex with TDP and the natural substrate, desvancosaminyl vancomycin.[1]
Identifiers
Symbol UDPGT
Pfam PF00201
InterPro IPR002213
PROSITE PDOC00359
SCOP 1rrv
SUPERFAMILY 1rrv

Uridine 5'-diphospho-glucuronosyltransferase (UDP-glucuronosyltransferase, UGT) is a glycosyltransferase (EC 2.4.1.17) that catalyzes the transfer of the glucuronic acid component of UDP-glucuronic acid to a small hydrophobic molecule. This is a glucuronidation reaction.[2]

Alternative names:

  • glucuronyltransferase
  • UDP-glucuronyl transferase
  • UDP-GT

Function[edit]

Main article: Glucuronidation

Glucuronosyltransferases are responsible for the process of glucuronidation, a major part of phase II metabolism. Arguably the most important of the Phase II (conjugative) enzymes, UGTs have been the subject of increasing scientific inquiry since the mid-to-late 1990s.

The reaction catalyzed by the UGT enzyme involves the addition of a glucuronic acid moiety to xenobiotics and is the most important pathway for the human body's elimination of the top 200 drugs. It is also the major pathway for foreign chemical (dietary, environmental, pharmaceutical) removal for most drugs, dietary substances, toxins and endogenous substances. UGT is present in humans, other animals, plants, and bacteria. Famously, UGT enzymes are not present in the genus Felis,[3] and this accounts for a number of unusual toxicities in the cat family.

The glucuronidation reaction consists of the transfer of the glucuronosyl group from uridine 5'-diphospho-glucuronic acid (UDPGA) to substrate molecules that contain oxygen, nitrogen, sulfur or carboxyl functional groups.[4] The resulting glucuronide is more polar (e.g. hydrophilic) and more easily excreted than the substrate molecule. The product solubility in blood is increased allowing it to be eliminated from the body by the kidneys.

Diseases[edit]

A deficiency in the bilirubin specific form of glucuronosyltransferase is thought to be the cause of Gilbert's syndrome, which is characterized by unconjugated hyperbilirubinemia.

It is also associated with Crigler-Najjar syndrome, a more serious disorder where the enzyme's activity is either completely absent (Crigler-Najjar syndrome type I) or less than 10% of normal (type II).

Infants may have a developmental deficiency in UDP-glucuronyl transferase, and are unable to hepatically metabolize the antibiotic drug chloramphenicol which requires glucuronidation. This leads to a condition known as gray baby syndrome.[5]

Genes[edit]

Human genes which encode UGT enzymes include:

References[edit]

  1. ^ Mulichak AM, Lu W, Losey HC, Walsh CT, Garavito RM (May 2004). "Crystal structure of vancosaminyltransferase GtfD from the vancomycin biosynthetic pathway: interactions with acceptor and nucleotide ligands". Biochemistry 43 (18): 5170–5180. doi:10.1021/bi036130c. PMID 15122882. 
  2. ^ King C, Rios G, Green M, Tephly T (2000). "UDP-glucuronosyltransferases". Curr Drug Metab 1 (2): 143–161. doi:10.2174/1389200003339171. PMID 11465080. 
  3. ^ Court MH and Greenblatt DJ (2000). "Molecular genetic basis for deficient acetaminophen glucuronidation by cats: UGT1A6 is a pseudogene, and evidence for reduced diversity of expressed hepatic UGT1A isoforms". Pharmacogenetics. 10 (4): 355–69. doi:10.1097/00008571-200006000-00009. PMID 10862526. 
  4. ^ Bock K, Köhle C (2005). "UDP-glucuronosyltransferase 1A6: structural, functional, and regulatory aspects". Methods Enzymol 400: 57–75. doi:10.1016/S0076-6879(05)00004-2. PMID 16399343. 
  5. ^ MacDougall, C; Chambers, HF (2011). "55". Protein Synthesis Inhibitors and Miscellaneous Antibacterial Agents. In: Brunton LL, Chabner BA, Knollmann BC, eds. Goodman & Gilman's The Pharmacological Basis of Therapeutics. (12 ed.). New York: McGraw-Hill. Retrieved October 19, 2011. 

External links[edit]