Publications

• Specificity and regioselectivity of the conjugation of estradiol, estrone, and their catecholestrogen and methoxyestrogen metabolites by human uridine diphospho-glucuronosyltransferases expressed in endometrium.

  Lepine J., Bernard O., Plante M., Tetu B., Pelletier G., Labrie F., Belanger A., Guillemette C.

  Uridine diphospho-glucuronosyltransferases (UGTs) inactivate and facilitate the excretion of estrogens to glucuronides (-G), the most abundant circulating estrogen conjugates. The identity of the conjugated estrogens formed by all known overexpressed UGTs (n = 16) was analyzed by comparison with r ... >> More

  Uridine diphospho-glucuronosyltransferases (UGTs) inactivate and facilitate the excretion of estrogens to glucuronides (-G), the most abundant circulating estrogen conjugates. The identity of the conjugated estrogens formed by all known overexpressed UGTs (n = 16) was analyzed by comparison with retention time and mass fragmentation of authentic standards by HPLC tandem mass spectrometry methods. Six UGTs, namely 1A1, 1A3, 1A8, 1A9, 1A10, and 2B7, were found to glucuronidate estradiol (E(2)) and estrone (E(1)), their hydroxyls (OH), and their methoxy derivatives (MeO). Addition of glucuronic acid was catalyzed by specific UGTs at positions 2, 3, and 4 of the estrogens, whereas only E(2) was conjugated at position 17 by UGT2B7. Kinetic parameters indicate that the conjugation of E(2) at position 3 was predominantly catalyzed by 1A1, 1A3, and 1A8 and by 1A8 for E(1). Conjugation of 2-OHE(1)/E(2) and 2- and 4-MeOE(1)/E(2) was selective at position 3, mostly catalyzed by 1A1 and 1A8. Of all UGTs, UGT2B7 demonstrated the highest catalytic activities for estrogens and at least 10-to 50-fold higher activity for the conjugation of genotoxic 4-hydroxycatecholestrogens at position 4, compared with the conjugation of E(2), E(1), and 2-hydroxycatecholestrogens. Its presence was further shown in the endometrium by RT-PCR and immunohistochemistry, localizing in the same cells expressing CYP1B1, involved locally in the formation of 4-hydroxycatecholestrogens. Data show that several UGT enzymes detected in the endometrium are involved in the glucuronidation of E(2) and its 2-OH, 4-OH, and 2-MeO metabolites that exert various biological effects in the tissue. << Less

  J. Clin. Endocrinol. Metab. 89:5222-5232(2004) [PubMed] [EuropePMC]

  This publication is cited by 13 other entries.

• Glucuronidation of estrone and 16alpha-hydroxyestrone by human UGT enzymes: The key roles of UGT1A10 and UGT2B7.

  Kallionpaeae R.A., Jaervinen E., Finel M.

  The glucuronidation of estrone and 16α-hydroxyestrone by recombinant human UDP-glucuronosyltransferase enzymes (UGTs) of subfamilies 1A, 2A and 2B was studied. Microsomes from human liver and small intestine were also tested for the glucuronidation of these two estrogens. The results revealed that ... >> More

  The glucuronidation of estrone and 16α-hydroxyestrone by recombinant human UDP-glucuronosyltransferase enzymes (UGTs) of subfamilies 1A, 2A and 2B was studied. Microsomes from human liver and small intestine were also tested for the glucuronidation of these two estrogens. The results revealed that UGT1A10 is by far the most active enzyme in estrone glucuronidation. UGT1A10 also exhibited high rate of 16α-hydroxyestrone conjugation at the 3-OH, whereas UGT2B7 catalyzed its glucuronidation at high rates at the 16-OH. Human liver microsomes exhibited high rates of 16α-hydroxyestrone-16-glucuronide formation, but very low formation rates of either 16α-hydroxyestrone-3-glucuronide or estrone glucuronide. On the other hand, human intestine microsomes catalyzed the formation of all these 3 different glucuronides at high rates. Kinetic analyses revealed very low Km value for 16α-hydroxyestrone glucuronidation by UGT2B7, below 4 μM, suggesting higher affinity than commonly found among UGTs and their substrates. In further studies with UGT1A10, mutant F93G exhibited increased glucuronidation rates of 16α-hydroxyestrone, but not estrone, whereas mutations in F90 did not reveal any activity with either estrogen. Taken together, the results of this study significantly expand our understanding on the metabolism of estrogens and their interactions with the human UGTs. << Less

  J. Steroid Biochem. Mol. Biol. 154:104-111(2015) [PubMed] [EuropePMC]

  This publication is cited by 2 other entries.

• Six novel UDP-glucuronosyltransferase (UGT1A3) polymorphisms with varying activity.

  Iwai M., Maruo Y., Ito M., Yamamoto K., Sato H., Takeuchi Y.

  Human UDP-glucuronosyltransferase (UGT) is a part of a major excretion pathway for endobiotics and xenobiotics. The UGT family of genes is highly polymorphic, and our aim is to describe novel polymorphisms at the UGT1A3 locus and determine how they alter substrate metabolism and drug reactions. On ... >> More

  Human UDP-glucuronosyltransferase (UGT) is a part of a major excretion pathway for endobiotics and xenobiotics. The UGT family of genes is highly polymorphic, and our aim is to describe novel polymorphisms at the UGT1A3 locus and determine how they alter substrate metabolism and drug reactions. One hundred healthy Japanese adults volunteered for the present study. We sequenced PCR-amplified fragments of the gene directly, and calculated the frequency of the genetic variations detected. To measure variant enzyme activity, we constructed five expression models and used estrone as the substrate in the assays. We identified six novel single nucleotide polymorphisms (SNPs). Of these, four caused amino acid substitutions (17A-->G: Q6R, 31T-->C: W11R, 133C-->T: R45W, and 140T-->C: V47A) and the remaining two were silent (81G-->A: E27E and 447A-->G: A159A). We found five types of alleles having differing SNP combinations: wild type (frequency=0.61), W11R-E27E-A159A (0.10), Q6A-W11R-E27E-A159A (0.055), W11R-E27E-V47A-A159A (0.125), and R45W (0.11). Expression studies found that the variants changed the enzyme efficiencies ( Km/ Vmax) to 121% of the wild type for W11R, 86% for Q6R-W11R, 369% for W11R-V47A, and 70% for R45W. Several UGT 1A3 polymorphisms exist in the Japanese population, having different levels of activity. These polymorphisms are capable of affecting the steady state levels of estrogens, and may increase sensitivity to adverse drug effects. << Less

  J Hum Genet 49:123-128(2004) [PubMed] [EuropePMC]