Six novel UDP-glucuronosyltransferase (UGT1A3) polymorphisms with varying activity.
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.
Iwai
Masaru
M
Department of Pediatrics, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
Maruo
Yoshihiro
Y
Department of Pediatrics, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan. maruo@belle.shiga-med.ac.jp.
Ito
Masaki
M
Department of Internal Medicine, Division of Gastroenterology, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
Yamamoto
Kazuo
K
Department of Clinical Laboratory Medicine, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
Sato
Hiroshi
H
Department of Bioscience, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
Takeuchi
Yoshihiro
Y
Department of Pediatrics, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
D000483:Alleles; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004970:Estrone / Q000494:pharmacology; D014644:Genetic Variation; D005822:Genetic Vectors; D014453:Glucuronosyltransferase / Q000235:genetics*; D006801:Humans; D007438:Introns; D007700:Kinetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D010957:Plasmids / Q000378:metabolism; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D020641:Polymorphism, Single Nucleotide; D020033:Protein Isoforms; D017422:Sequence Analysis, DNA; D013997:Time Factors; D014162:Transfection
D018076:DNA, Complementary; D020033:Protein Isoforms; D004970:Estrone; C122075:UDP-glucuronosyltransferase, UGT1A3; D014453:Glucuronosyltransferase