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Six novel UDP-glucuronosyltransferase (UGT1A3) polymorphisms with varying activity
Masaru Iwai1, Yoshihiro Maruo2, Masaki Ito3
1Department of Pediatrics, Shiga University of Medical Science, Otsu, Shiga 520-2192, Japan.
Journal of Human Genetics
|February 27, 2004
Summary
Novel genetic variations in human UDP-glucuronosyltransferase (UGT) 1A3 were identified in Japanese adults. These UGT1A3 polymorphisms significantly alter enzyme activity, potentially impacting drug metabolism and estrogen levels.
Area of Science:
- Pharmacogenomics
- Drug Metabolism
- Enzyme Kinetics
Background:
- Human UDP-glucuronosyltransferase (UGT) enzymes are crucial for eliminating endogenous and exogenous compounds.
- The UGT gene family exhibits significant genetic diversity (polymorphisms).
- Understanding UGT1A3 variations is key to predicting drug response and toxicity.
Purpose of the Study:
- To identify and characterize novel polymorphisms in the UGT1A3 gene.
- To investigate the functional impact of these UGT1A3 variants on enzyme activity.
- To assess the potential clinical implications of UGT1A3 polymorphisms in drug metabolism.
Main Methods:
- Direct sequencing of PCR-amplified UGT1A3 gene fragments in 100 healthy Japanese adults.
- Identification and frequency calculation of single nucleotide polymorphisms (SNPs).
- Construction of expression models to measure variant enzyme activity using estrone as a substrate.
Main Results:
- Six novel SNPs were identified in the UGT1A3 gene, including four leading to amino acid substitutions.
- Five distinct UGT1A3 alleles were characterized based on SNP combinations, with varying frequencies.
- Enzyme kinetic studies revealed significant alterations in enzyme efficiency (Km/Vmax) for several variants, including W11R (121%) and W11R-V47A (369% of wild type).
Conclusions:
- The Japanese population harbors diverse UGT1A3 polymorphisms with differential enzyme activities.
- These UGT1A3 genetic variations can influence the metabolic clearance of substrates like estrogens.
- The identified polymorphisms may predispose individuals to altered drug efficacy and increased sensitivity to adverse drug reactions.