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cDNA cloning and characterization of the human UDP glucuronosyltransferase, UGT1A3
B Mojarrabi1, R Butler, P I Mackenzie
1Department of Clinical Pharmacology, Flinders Medical Centre, Bedford Park, Australia.
Abstract:
The cDNA encoding the UDP glucuronosyltransferase, UGT1A3, has been cloned and expressed in cell culture. The deduced amino acid sequence of the cDNA is 90% similar in sequence to that of a previously characterized form, UGT1A4 and to that of a third form, UGT1A5 whose function in unknown. UGT1A3, when expressed in COS cells has a relative molecular mass of 55 kDa and is active in the glucuronidation of estrone and 2-hydroxyestrone. Activity towards other polyhydroxylated estrogens including 4-hydroxyestrogen and estriol and its metabolites was not detected. UGT1A3 was also inactive towards androgens and their metabolites. The enzyme preferentially glucuronidated the N-hydroxy metabolite of 2-acetylaminofluorence and was more active towards the 6- and 12-hydroxylated metabolites of benzo[alpha]pyrene. RNA encoding UGT1A3 was detected in human liver and colon tissue.