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Xue J, Yin J, Nie J, Jiang H, Zhang H, Zeng S. Heterodimerization of Human UDP-Glucuronosyltransferase 1A9 and UDP-Glucuronosyltransferase 2B7 Alters Their Glucuronidation Activities. Drug Metab Dispos 2023; 51:1499-1507. [PMID: 37643881 DOI: 10.1124/dmd.123.001369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Revised: 08/21/2023] [Accepted: 08/22/2023] [Indexed: 08/31/2023] Open
Abstract
Human UDP-glucuronosyltransferases (UGTs) play a pivotal role as prominent phase II metabolic enzymes, mediating the glucuronidation of both endobiotics and xenobiotics. Dimerization greatly modulates the enzymatic activities of UGTs. In this study, we examined the influence of three mutations (H35A, H268Y, and N68A/N315A) and four truncations (signal peptide, single transmembrane helix, cytosolic tail, and di-lysine motif) in UGT2B7 on its heterodimerization with wild-type UGT1A9, using a Bac-to-Bac expression system. We employed quantitative fluorescence resonance energy transfer (FRET) techniques and co-immunoprecipitation assays to evaluate the formation of heterodimers between UGT1A9 and UGT2B7 allozymes. Furthermore, we evaluated the glucuronidation activities of the heterodimers using zidovudine and propofol as substrates for UGT2B7 and UGT1A9, respectively. Our findings revealed that the histidine residue at codon 35 was involved in the dimeric interaction, as evidenced by the FRET efficiencies and catalytic activities. Interestingly, the signal peptide and single transmembrane helix domain of UGT2B7 had no impact on the protein-protein interaction. These results provide valuable insights for a comprehensive understanding of UGT1A9/UGT2B7 heterodimer formation and its association with glucuronidation activity. SIGNIFICANCE STATEMENT: Our findings revealed that the H35A mutation in UGT2B7 affected the affinity of protein-protein interaction, leading to discernable variations in fluorescence resonance energy transfer efficiencies and catalytic activity. Furthermore, the signal peptide and single transmembrane helix domain of UGT2B7 did not influence heterodimer formation. These results provide valuable insights into the combined effects of polymorphisms and protein-protein interactions on the catalytic activity of UGT1A9 and UGT2B7, enhancing our understanding of UGT dimerization and its impact on metabolite formation.
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Affiliation(s)
- Jia Xue
- Institute of Drug Metabolism and Pharmaceutical Analysis (J.X., J.Y., J.N., H.J., S.Z.) and Hangzhou Institute of Innovative Medicine, Institute of Pharmacology and Toxicology (H.Z.), Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China; Department of Pharmacy, Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China (J.N.); and The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China (H.Z.)
| | - Jiayi Yin
- Institute of Drug Metabolism and Pharmaceutical Analysis (J.X., J.Y., J.N., H.J., S.Z.) and Hangzhou Institute of Innovative Medicine, Institute of Pharmacology and Toxicology (H.Z.), Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China; Department of Pharmacy, Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China (J.N.); and The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China (H.Z.)
| | - Jing Nie
- Institute of Drug Metabolism and Pharmaceutical Analysis (J.X., J.Y., J.N., H.J., S.Z.) and Hangzhou Institute of Innovative Medicine, Institute of Pharmacology and Toxicology (H.Z.), Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China; Department of Pharmacy, Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China (J.N.); and The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China (H.Z.)
| | - Huidi Jiang
- Institute of Drug Metabolism and Pharmaceutical Analysis (J.X., J.Y., J.N., H.J., S.Z.) and Hangzhou Institute of Innovative Medicine, Institute of Pharmacology and Toxicology (H.Z.), Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China; Department of Pharmacy, Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China (J.N.); and The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China (H.Z.)
| | - Haitao Zhang
- Institute of Drug Metabolism and Pharmaceutical Analysis (J.X., J.Y., J.N., H.J., S.Z.) and Hangzhou Institute of Innovative Medicine, Institute of Pharmacology and Toxicology (H.Z.), Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China; Department of Pharmacy, Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China (J.N.); and The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China (H.Z.)
| | - Su Zeng
- Institute of Drug Metabolism and Pharmaceutical Analysis (J.X., J.Y., J.N., H.J., S.Z.) and Hangzhou Institute of Innovative Medicine, Institute of Pharmacology and Toxicology (H.Z.), Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China; Department of Pharmacy, Children's Hospital, Zhejiang University School of Medicine, National Clinical Research Center for Child Health, Hangzhou, Zhejiang, China (J.N.); and The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China (H.Z.)
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Hetero-oligomer formation of mouse UDP-glucuronosyltransferase (UGT) 2b1 and 1a1 results in the gain of glucuronidation activity towards morphine, an activity which is absent in homo-oligomers of either UGT. Biochem Biophys Res Commun 2020; 525:348-353. [PMID: 32093886 DOI: 10.1016/j.bbrc.2020.02.075] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Accepted: 02/11/2020] [Indexed: 01/11/2023]
Abstract
UDP-Glucuronosyltransferase (UGT, Ugt) is a major drug metabolizing enzyme family involved in the glucuronidation and subsequent elimination of drugs and small lipophilic molecules. UGT forms homo- and hetero-oligomers that enhance or suppress UGT activity. In our previous study, we characterized mouse Ugt1a1 and all the Ugt isoform belonging to the Ugt2b subfamily and revealed that mouse Ugt2b1 and Ugt1a1 cannot metabolize morphine. Mouse Ugt2b1 had been believed to function similarly to rat UGT2B1, which plays a major role in morphine glucuronidation in rat liver. Thus, in this study, we hypothesized that hetero-oligomerization with another Ugt isoform may affect Ugt2b1 catalytic ability. We co-expressed Ugt1a1 and Ugt2b1 in a baculovirus-insect cell system, and confirmed hetero-oligomer formation by co-immunoprecipitation. As reported previously, microsomes singly expressing Ugt1a1 or Ugt2b1 were inactive towards the glucuronidation of morphine. Interestingly, in contrast, morphine-3-glucuronide, a major metabolite of morphine was formed, when Ugt2b1 and Ugt1a1 were co-expressed. This effect of hetero-oligomerization of Ugt1a1 and Ugt2b1 was also observed for 17β-estradiol glucuronidation. This is the first report demonstrating that UGT acquires a novel catalytic ability by forming oligomers. Protein-protein interaction of Ugts may contribute to robust detoxification of xenobiotics by altering the substrate diversity of the enzymes.
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Meech R, Hu DG, McKinnon RA, Mubarokah SN, Haines AZ, Nair PC, Rowland A, Mackenzie PI. The UDP-Glycosyltransferase (UGT) Superfamily: New Members, New Functions, and Novel Paradigms. Physiol Rev 2019; 99:1153-1222. [DOI: 10.1152/physrev.00058.2017] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
UDP-glycosyltransferases (UGTs) catalyze the covalent addition of sugars to a broad range of lipophilic molecules. This biotransformation plays a critical role in elimination of a broad range of exogenous chemicals and by-products of endogenous metabolism, and also controls the levels and distribution of many endogenous signaling molecules. In mammals, the superfamily comprises four families: UGT1, UGT2, UGT3, and UGT8. UGT1 and UGT2 enzymes have important roles in pharmacology and toxicology including contributing to interindividual differences in drug disposition as well as to cancer risk. These UGTs are highly expressed in organs of detoxification (e.g., liver, kidney, intestine) and can be induced by pathways that sense demand for detoxification and for modulation of endobiotic signaling molecules. The functions of the UGT3 and UGT8 family enzymes have only been characterized relatively recently; these enzymes show different UDP-sugar preferences to that of UGT1 and UGT2 enzymes, and to date, their contributions to drug metabolism appear to be relatively minor. This review summarizes and provides critical analysis of the current state of research into all four families of UGT enzymes. Key areas discussed include the roles of UGTs in drug metabolism, cancer risk, and regulation of signaling, as well as the transcriptional and posttranscriptional control of UGT expression and function. The latter part of this review provides an in-depth analysis of the known and predicted functions of UGT3 and UGT8 enzymes, focused on their likely roles in modulation of levels of endogenous signaling pathways.
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Affiliation(s)
- Robyn Meech
- Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, South Australia, Australia
| | - Dong Gui Hu
- Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, South Australia, Australia
| | - Ross A. McKinnon
- Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, South Australia, Australia
| | - Siti Nurul Mubarokah
- Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, South Australia, Australia
| | - Alex Z. Haines
- Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, South Australia, Australia
| | - Pramod C. Nair
- Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, South Australia, Australia
| | - Andrew Rowland
- Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, South Australia, Australia
| | - Peter I. Mackenzie
- Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University College of Medicine and Public Health, Flinders Medical Centre, Bedford Park, South Australia, Australia
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Fujiwara R, Yokoi T, Nakajima M. Structure and Protein-Protein Interactions of Human UDP-Glucuronosyltransferases. Front Pharmacol 2016; 7:388. [PMID: 27822186 PMCID: PMC5075577 DOI: 10.3389/fphar.2016.00388] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 10/05/2016] [Indexed: 12/11/2022] Open
Abstract
Mammalian UDP-glucuronosyltransferases (UGTs) catalyze the transfer of glucuronic acid from UDP-glucuronic acid to various xenobiotics and endobiotics. Since UGTs comprise rate-limiting enzymes for metabolism of various compounds, co-administration of UGT-inhibiting drugs and genetic deficiency of UGT genes can cause an increased blood concentration of these compounds. During the last few decades, extensive efforts have been made to advance the understanding of gene structure, function, substrate specificity, and inhibition/induction properties of UGTs. However, molecular mechanisms and physiological importance of the oligomerization and protein–protein interactions of UGTs are still largely unknown. While three-dimensional structures of human UGTs can be useful to reveal the details of oligomerization and protein–protein interactions of UGTs, little is known about the protein structures of human UGTs due to the difficulty in solving crystal structures of membrane-bound proteins. Meanwhile, soluble forms of plant and bacterial UGTs as well as a partial domain of human UGT2B7 have been crystallized and enabled us to predict three-dimensional structures of human UGTs using a homology-modeling technique. The homology-modeled structures of human UGTs do not only provide the detailed information about substrate binding or substrate specificity in human UGTs, but also contribute with unique knowledge on oligomerization and protein–protein interactions of UGTs. Furthermore, various in vitro approaches indicate that UGT-mediated glucuronidation is involved in cell death, apoptosis, and oxidative stress as well. In the present review article, recent understandings of UGT protein structures as well as physiological importance of the oligomerization and protein–protein interactions of human UGTs are discussed.
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Affiliation(s)
- Ryoichi Fujiwara
- Department of Pharmaceutics, School of Pharmacy, Kitasato University Tokyo, Japan
| | - Tsuyoshi Yokoi
- Department of Drug Safety Sciences, Division of Clinical Pharmacology, Nagoya University Graduate School of Medicine Nagoya, Japan
| | - Miki Nakajima
- Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University Kanazawa, Japan
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Konopnicki CM, Dickmann LJ, Tracy JM, Tukey RH, Wienkers LC, Foti RS. Evaluation of UGT protein interactions in human hepatocytes: effect of siRNA down regulation of UGT1A9 and UGT2B7 on propofol glucuronidation in human hepatocytes. Arch Biochem Biophys 2013; 535:143-9. [PMID: 23562620 DOI: 10.1016/j.abb.2013.03.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 03/21/2013] [Accepted: 03/22/2013] [Indexed: 12/11/2022]
Abstract
Previous experiments performed in recombinant systems have suggested that protein-protein interactions occur between the UGTs and may play a significant role in modulating enzyme activity. However, evidence of UGT protein-protein interactions either in vivo or in more physiologically relevant in vitro systems has yet to be demonstrated. In this study, we examined oligomerization and its ability to affect glucuronidation in plated human hepatocytes. siRNA down regulation experiments and activity studies were used to examine changes in metabolite formation of one UGT isoform due to down regulation of a second UGT isoform. Selective siRNA directed towards UGT1A9 or UGT2B7 resulted in significant and selective decreases in their respective mRNA levels. As expected, the metabolism of the UGT1A9 substrate propofol decreased with UGT1A9 down regulation. Interestingly, UGT1A9 activity, but not UGT1A9 mRNA expression, was also diminished when UGT2B7 expression was selectively inhibited, implying potential interactions between the two isoforms. Minor changes to UGT1A4, UGT2B4 and UGT2B7 activity were also observed when UGT1A9 expression was selectively down regulated. To our knowledge, this represents the first piece of evidence that UGT protein-protein interactions occur in human hepatocytes and suggests that expression levels of UGT2B7 may directly impact the glucuronidation activity of selective UGT1A9 substrates.
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Affiliation(s)
- Camille M Konopnicki
- Department of Chemistry and Biochemistry, University of California, 9500 Gilman Drive La Jolla, San Diego, CA 92093, USA
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Protein-protein interactions between the bilirubin-conjugating UDP-glucuronosyltransferase UGT1A1 and its shorter isoform 2 regulatory partner derived from alternative splicing. Biochem J 2013; 450:107-14. [PMID: 23148825 DOI: 10.1042/bj20121594] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The oligomerization of UGTs [UDP (uridine diphosphate)-glucuronosyltransferases] modulates their enzyme activities. Recent findings also indicate that glucuronidation is negatively regulated by the formation of inactive oligomeric complexes between UGT1A enzymes [i1 (isoform 1)] and an enzymatically inactive alternatively spliced i2 (isoform 2). In the present paper, we assessed whether deletion of the UGT-interacting domains previously reported to be critical for enzyme function might be involved in i1-i2 interactions. The bilirubin-conjugating UGT1A1 was used as a prototype. We also explored whether intermolecular disulfide bonds are involved in i1-i2 interactions and the potential role of selected cysteine residues. Co-immunoprecipitation assays showed that UGT1A1 lacking the SP (signal peptide) alone or also lacking the transmembrane domain (absent from i2) did not self-interact, but still interacted with i2. The deletion of other N- or C-terminal domains did not compromise i1-i2 complex formation. Under non-reducing conditions, we also observed formation of HMWCs (high-molecular-mass complexes) for cells overexpressing i1 and i2. The presence of UGTs in these complexes was confirmed by MS. Mutation of individual cysteine residues throughout UGT1A1 did not compromise i1-i1 or i1-i2 complex formation. These findings are compatible with the hypothesis that the interaction between i1 and i2 proteins (either transient or stable) involves binding of more than one domain that probably differs from those involved in i1-i1 interactions.
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Tripathi SP, Bhadauriya A, Patil A, Sangamwar AT. Substrate selectivity of human intestinal UDP-glucuronosyltransferases (UGTs): in silico and in vitro insights. Drug Metab Rev 2013; 45:231-52. [PMID: 23461702 DOI: 10.3109/03602532.2013.767345] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The current drug development process aims to produce safe, effective drugs within a reasonable time and at a reasonable cost. Phase II metabolism (glucuronidation) can affect drug action and pharmacokinetics to a considerable extent and so its studies and prediction at initial stages of drug development are very imperative. Extensive glucuronidation is an obstacle to oral bioavailability because the first-pass glucuronidation [or premature clearance by UDP-glucuronosyltransferases (UGTs)] of orally administered agents frequently results in poor oral bioavailability and lack of efficacy. Modeling of new chemical entities/drugs for UGTs and their kinetic data can be useful in understanding the binding patterns to be used in the design of better molecules. This review concentrates on first-pass glucuronidation by intestinal UGTs, including their topology, expression profile, and pharmacogenomics. In addition, recent advances are discussed with respect to substrate selectivity at the binding pocket, structural requirements, and mechanism of enzyme actions.
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Affiliation(s)
- Satya Prakash Tripathi
- Department of Pharmacoinformatics, National Institute of Pharmaceutical Education and Research (NIPER), Punjab, India
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Manevski N, Troberg J, Svaluto-Moreolo P, Dziedzic K, Yli-Kauhaluoma J, Finel M. Albumin stimulates the activity of the human UDP-glucuronosyltransferases 1A7, 1A8, 1A10, 2A1 and 2B15, but the effects are enzyme and substrate dependent. PLoS One 2013; 8:e54767. [PMID: 23372764 PMCID: PMC3553014 DOI: 10.1371/journal.pone.0054767] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/14/2012] [Indexed: 12/05/2022] Open
Abstract
Human UDP-glucuronosyltransferases (UGTs) are important enzymes in metabolic elimination of endo- and xenobiotics. It was recently shown that addition of fatty acid free bovine serum albumin (BSA) significantly enhances in vitro activities of UGTs, a limiting factor in in vitro–in vivo extrapolation. Nevertheless, since only few human UGT enzymes were tested for this phenomenon, we have now performed detailed enzyme kinetic analysis on the BSA effects in six previously untested UGTs, using 2–4 suitable substrates for each enzyme. We also examined some of the previously tested UGTs, but using additional substrates and a lower BSA concentration, only 0.1%. The latter concentration allows the use of important but more lipophilic substrates, such as estradiol and 17-epiestradiol. In five newly tested UGTs, 1A7, 1A8, 1A10, 2A1, and 2B15, the addition of BSA enhanced, to a different degree, the in vitro activity by either decreasing reaction’s Km, increasing its Vmax, or both. In contrast, the activities of UGT2B17, another previously untested enzyme, were almost unaffected. The results of the assays with the previously tested UGTs, 1A1, 1A6, 2B4, and 2B7, were similar to the published BSA only as far as the BSA effects on the reactions’ Km are concerned. In the cases of Vmax values, however, our results differ significantly from the previously published ones, at least with some of the substrates. Hence, the magnitude of the BSA effects appears to be substrate dependent, especially with respect to Vmax increases. Additionally, the BSA effects may be UGT subfamily dependent since Km decreases were observed in members of subfamilies 1A, 2A and 2B, whereas large Vmax increases were only found in several UGT1A members. The results shed new light on the complexity of the BSA effects on the activity and enzyme kinetics of the human UGTs.
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Affiliation(s)
- Nenad Manevski
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
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Human UDP-glucuronosyltransferase UGT2A2: cDNA construction, expression, and functional characterization in comparison with UGT2A1 and UGT2A3. Pharmacogenet Genomics 2012; 19:923-34. [PMID: 19858781 DOI: 10.1097/fpc.0b013e3283330767] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES Characterize the expression and glucuronidation activities of the human uridine 5'-diphospho (UDP)-glucuronosyltransferase (UGT) 2A2. METHOD UGT2A1 was cloned from nasal mucosa mRNA. Synthetic cDNA for UGT2A2 was constructed assuming exon sharing between UGT2A1 and UGT2A2 (Mackenzie et al., Pharmacogenetics and Genomics 2005, 15:677-685). Exon 1 of UGT2A2 was amplified from genomic DNA and combined with exons 2-6 of UGT2A1. UGT2A3 was cloned from liver mRNA. Quantitative reverse-transcribed-PCR (RT-PCR) was used to evaluate the expression of all the three UGTs of subfamily 2A in different tissues. Recombinant UGT2A1, UGT2A2 and UGT2A3 were expressed in baculovirus-infected insect cells and analyzed for glucuronidation activity towards different substrates. RESULTS DNA sequencing of RT-PCR products from human nasal mucosa mRNA, confirmed exon sharing between UGT2A1 and UGT2A2. In addition, it indicated that the N-terminal signal peptide sequence of UGT2A2 is the longest among the human UGTs. Quantitative RT-PCR revealed that both UGT2A1 and UGT2A2 are mainly expressed in the nasal mucosa, and that their expression level in fetal samples was much higher than in adults. Activity assays with recombinant UGTs 2A1-2A3 showed broad substrate selectivity for UGT2A1 and UGT2A2. Although glucuronidation rates and substrate affinities were mostly higher in UGT2A1, the Km values for UDP-glucuronic acid were similar in both UGTs. In addition, there were regioselectivity differences between the two UGTs and, with a few substrates, particularly ethinylestradiol, the activity of UGT2A2 was higher. CONCLUSION UGT2A2 is mainly expressed in the nasal mucosa and it has glucuronidation activity towards several different endobiotic and xenobiotic substrates.
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Zhang H, Patana AS, Mackenzie PI, Ikushiro S, Goldman A, Finel M. Human UDP-Glucuronosyltransferase Expression in Insect Cells: Ratio of Active to Inactive Recombinant Proteins and the Effects of a C-Terminal His-Tag on Glucuronidation Kinetics. Drug Metab Dispos 2012; 40:1935-44. [DOI: 10.1124/dmd.112.046086] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
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Höglund C, Sneitz N, Radominska-Pandya A, Laakonen L, Finel M. Phenylalanine 93 of the human UGT1A10 plays a major role in the interactions of the enzyme with estrogens. Steroids 2011; 76:1465-73. [PMID: 21846474 PMCID: PMC3188330 DOI: 10.1016/j.steroids.2011.07.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 07/28/2011] [Accepted: 07/29/2011] [Indexed: 10/17/2022]
Abstract
Little is currently known about the substrate binding site of the human UDP-glucuronosyltransferases (UGTs) and the structural elements that affect their complex substrate selectivity. In order to further understand and extend our earlier findings with phenylalanines 90 and 93 of UGT1A10, we have replaced each of them with Gly, Ala, Val, Leu, Ile or Tyr, and tested the activity of the resulting 12 mutants toward eight different substrates. Apart from scopoletin glucuronidation, the F90 mutants other than F90L were nearly inactive, while the F93 mutants' activity was strongly substrate dependent. Hence, F93L displayed high entacapone and 1-naphthol glucuronidation rates, whereas F93G, which was nearly inactive in entacapone glucuronidation, was highly active toward estradiol, estriol and even ethinylestradiol, a synthetic estrogen that is a poor substrate for the wild-type UGT1A10. Kinetic analyses of 4-nitrophenol, estradiol and ethinylestradiol glucuronidation by the mutants that catalyzed the respective reactions at considerable rates, revealed increased K(m) values for 4-nitrophenol and estradiol in all the mutants, whilst the K(m) values of F93G and F93A for ethinylestradiol were lower than in control UGT1A10. Based on the activity results and a new molecular model of UGT1A10, it is suggested that both F90 and F93 are located in a surface helix at the far end of the substrate binding site. Nevertheless, only F93 directly affects the selectivity of UGT1A10 toward large and rigid estrogens, particularly those with substitutions at the D ring. The effects of F93 mutations on the glucuronidation of smaller or less rigid substrates are indirect, however.
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Affiliation(s)
- Camilla Höglund
- Centre for Drug Research, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5), FI-00014 University of Helsinki, Finland
- Division of Pharmaceutical Chemistry, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5), FI-00014 University of Helsinki, Finland
| | - Nina Sneitz
- Centre for Drug Research, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5), FI-00014 University of Helsinki, Finland
- Division of Pharmaceutical Chemistry, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5), FI-00014 University of Helsinki, Finland
| | - Anna Radominska-Pandya
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, Arkansas, USA (A.R.-P.)
| | - Liisa Laakonen
- Centre for Drug Research, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5), FI-00014 University of Helsinki, Finland
| | - Moshe Finel
- Centre for Drug Research, Faculty of Pharmacy, P.O. Box 56 (Viikinkaari 5), FI-00014 University of Helsinki, Finland
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Lewis BC, Mackenzie PI, Miners JO. Homodimerization of UDP-glucuronosyltransferase 2B7 (UGT2B7) and identification of a putative dimerization domain by protein homology modeling. Biochem Pharmacol 2011; 82:2016-23. [DOI: 10.1016/j.bcp.2011.09.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Revised: 09/05/2011] [Accepted: 09/06/2011] [Indexed: 01/25/2023]
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Compound heterozygote of a novel missense mutation (p.K402T) and a double missense mutation (p.[G71R;Y486D]) in type II Crigler-Najjar syndrome. J Pediatr Gastroenterol Nutr 2011; 52:362-5. [PMID: 21297505 DOI: 10.1097/mpg.0b013e3181fcafb8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Bellemare J, Rouleau M, Girard H, Harvey M, Guillemette C. Alternatively Spliced Products of the UGT1A Gene Interact with the Enzymatically Active Proteins to Inhibit Glucuronosyltransferase Activity In Vitro. Drug Metab Dispos 2010; 38:1785-9. [DOI: 10.1124/dmd.110.034835] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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Ishii Y, Takeda S, Yamada H. Modulation of UDP-glucuronosyltransferase activity by protein-protein association. Drug Metab Rev 2010; 42:145-58. [PMID: 19817679 DOI: 10.3109/03602530903208579] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Drug oxidation and conjugation mediated by cytochrome P450 (P450) and UDP-glucuronosyltransferase (UGT) have long been considered to take place separately. However, our recent studies have suggested that CYP3A4 specifically associates with UGT2B7 and alters the regioselectivity of morphine glucuronidation. This observation strongly supports the view that there is functional cooperation between P450 and UGT to facilitate multistep drug metabolism. In recent years, accumulating evidence has suggested an interaction between UGT isoforms or between P450 and UGTs and a change in UGT function by protein-protein association. In this review, we summarize these interactions and discuss their relevance to UGT function.
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Affiliation(s)
- Yuji Ishii
- Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan.
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16
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Laakkonen L, Finel M. A molecular model of the human UDP-glucuronosyltransferase 1A1, its membrane orientation, and the interactions between different parts of the enzyme. Mol Pharmacol 2010; 77:931-9. [PMID: 20215562 DOI: 10.1124/mol.109.063289] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The vertebrate UDP-glucuronosyltransferases (UGTs) are membrane-bound enzymes of the endoplasmic reticulum that process both endogenous and exogenous substrates. The human UGTs are well known biologically, but biophysical understanding is scarce, largely because of problems in purification. The one resolved crystal structure covers the C-terminal domain of the human UGT2B7. Here, we present a homology model of the complete monomeric human UGT1A1, the enzyme that catalyzes bilirubin glucuronidation. The enzyme can be seen as composed of four different domains: two large ones, the N- and C-terminal domains, and two small ones, the "envelope" helices and the transmembrane segment that includes the cytoplasmic tail. The hydrophobic core of the N-terminal domain and the two envelope helices that connect the large domains are shown to be structurally well conserved even among distant homologs and can thus be modeled with good certainty according to plant and bacterial structures. We consider alternative solutions for the highly variable N-terminal regions that probably contribute to substrate binding. The bilirubin binding site, known pathological mutations in UGT1A1, and other specific residues have been examined in the context of the model with regard to available experimental data. A putative orientation of the protein relative to the membrane has been derived from the location of predicted N-glycosylation sites. The model presents extensive interactions between the N- and C-terminal domains, the two envelope helices, and the membrane. Together, these interactions could allow for a concerted large-scale conformational change during catalysis.
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Affiliation(s)
- Liisa Laakkonen
- Centre for Drug Research, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
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17
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Fujiwara R, Nakajima M, Oda S, Yamanaka H, Ikushiro SI, Sakaki T, Yokoi T. Interactions between human UDP-glucuronosyltransferase (UGT) 2B7 and UGT1A enzymes. J Pharm Sci 2010; 99:442-54. [DOI: 10.1002/jps.21830] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Guillemette C, Lévesque E, Harvey M, Bellemare J, Menard V. UGT genomic diversity: beyond gene duplication. Drug Metab Rev 2009; 42:24-44. [DOI: 10.3109/03602530903210682] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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19
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Fujiwara R, Nakajima M, Yamanaka H, Yokoi T. Key Amino Acid Residues Responsible for the Differences in Substrate Specificity of Human UDP-Glucuronosyltransferase (UGT)1A9 and UGT1A8. Drug Metab Dispos 2008; 37:41-6. [DOI: 10.1124/dmd.108.022913] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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20
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Itäaho K, Mackenzie PI, Ikushiro SI, Miners JO, Finel M. The Configuration of the 17-Hydroxy Group Variably Influences the Glucuronidation of β-Estradiol and Epiestradiol by Human UDP-Glucuronosyltransferases. Drug Metab Dispos 2008; 36:2307-15. [DOI: 10.1124/dmd.108.022731] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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21
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Takahashi H, Maruo Y, Mori A, Iwai M, Sato H, Takeuchi Y. Effect of D256N and Y483D on Propofol Glucuronidation by Human Uridine 5′-diphosphate Glucuronosyltransferase (UGT1A9). Basic Clin Pharmacol Toxicol 2008; 103:131-6. [DOI: 10.1111/j.1742-7843.2008.00247.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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22
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Patana AS, Kurkela M, Finel M, Goldman A. Mutation analysis in UGT1A9 suggests a relationship between substrate and catalytic residues in UDP-glucuronosyltransferases. Protein Eng Des Sel 2008; 21:537-43. [PMID: 18502788 DOI: 10.1093/protein/gzn030] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
UDP-glucuronosyltransferases (UGTs) catalyze the transfer of glucuronic acid from UDP-glucuronic acid to endo- and xenobiotics in our body. UGTs belong to the GT1 family of glycosyltransferases and many GT1s use a serine protease-like catalytic mechanism in which an Asp-His pair deprotonates a hydroxyl on the aglycone for nucleophilic attack on the sugar donor. The pair in human UGTs could be H37 and either D143 or D148 (UGT1A9 numbering). However, H37 is not totally conserved, being replaced by either Pro or Leu in UGT1A4 and UGT2B10. We therefore investigated the role of H37, D143 and D148 in UGT1A9 by site-directed mutagenesis, activity and kinetic measurements with several substrates. The results suggest that H37 is not critical in N-glucuronidation, but is so in O-glucuronidation. The V(max) of the H37A mutant was much less affected in N- than O-glucuronidation, while the reverse was true for the Asp mutations, particularly D143A. We suggest that this is due to the opposing properties of O- and N- nucleophiles. O-nucleophiles require the histidine to deprotonate them so that they become effective nucleophiles, while N-nucleophiles develop a formal positive charge during the reaction (RNH(2)(+)-GlcA), and thus require a negatively charged residue to stabilize the transition state.
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Affiliation(s)
- Anne-Sisko Patana
- Structural Biology and Biophysics, Institute of Biotechnology, University of Helsinki, Biocenter 3, PO Box 65, Viikinkaari 1, FIN-00014 Helsinki, Finland
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23
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Influence of mutations associated with Gilbert and Crigler-Najjar type II syndromes on the glucuronidation kinetics of bilirubin and other UDP-glucuronosyltransferase 1A substrates. Pharmacogenet Genomics 2008; 17:1017-29. [PMID: 18004206 DOI: 10.1097/fpc.0b013e328256b1b6] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVES UGT1A1 coding region mutations, including UGT1A1*6 (G71R), UGT1A1*7 (Y486D), UGT1A1*27 (P229Q) and UGT1A1*62 (F83L), have been linked to Gilbert syndrome in Asian populations, whereas homozygosity for UGT1A1*7 is associated with the Crigler-Najjar syndrome type II. This work compared the effects of (a) the individual UGT1A1 mutations on the glucuronidation kinetics bilirubin, beta-estradiol, 4-methylumbelliferone (4MU) and 1-naphthol (1NP), and (b) the Y486 mutation, which occurs in the conserved carboxyl terminal domain of UGT1A enzymes, on 4MU, 1NP and naproxen glucuronidation by UGT1A3, UGT1A6 and UGT1A10. METHODS Mutant UGT1A cDNAs were generated by site-directed mutagenesis and the encoded proteins were expressed in HEK293 cells. The glucuronidation kinetics of each substrate with each enzyme were characterized using specific high-performance liquid chromatography (HPLC) methods. RESULTS Compared with wild-type UGT1A1, in-vitro clearances for bilirubin, beta-estradiol, 4MU and 1NP glucuronidation by UGT1A1*6 and UGT1A1*27 were reduced by 34-74%, most commonly as a result of a reduction in Vmax. However, the magnitude of the decrease in the in-vitro clearances varied from substrate to substrate with each mutant. The glucuronidation activities of UGT1A1*7 and UGT1A1*62 were reduced by >95%. Introduction of the Y486D mutation essentially abolished UGT1A6 and UGT1A10 activities, and resulted in 60-90% reductions in UGT1A3 in-vitro clearances. CONCLUSIONS The glucuronidation of all UGT1A1 substrates is likely to be impaired in subjects carrying the UGT1A1*6 and UGT1A1*62 alleles, although the reduction in metabolic clearance might vary with the substrate. The Y486D mutation appears to greatly reduce most, but not all, UGT1A activities.
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Fujiwara R, Nakajima M, Yamanaka H, Katoh M, Yokoi T. Interactions between Human UGT1A1, UGT1A4, and UGT1A6 Affect Their Enzymatic Activities. Drug Metab Dispos 2007; 35:1781-7. [PMID: 17620344 DOI: 10.1124/dmd.107.016402] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Protein-protein interactions between human UDP-glucuronosyltransferase (UGT) 1A1, UGT1A4, and UGT1A6 were investigated using double expression systems in HEK293 cells (UGT1A1/UGT1A4, UGT1A1/UGT1A6, and UGT1A4/UGT1A6). The substrates specific for UGT1A1 (estradiol and bilirubin), UGT1A4 (imipramine and trifluoperazine), and UGT1A6 (serotonin and diclofenac) were used to determine the effects of the coexpression of the other UGT1A isoforms on the enzymatic activity. The coexpression of UGT1A4 and UGT1A6 decreased the S(50) and V(max) values of UGT1A1-catalyzed estradiol 3-O-glucuronide formation and increased the V(max) value of UGT1A1-catalyzed bilirubin O-glucuronide formation. The coexpression of UGT1A1 decreased the V(max) value of UGT1A4-catalyzed imipramine N-glucuronide formation but had no effect on UGT1A4-catalyzed trifluoperazine N-glucuronide formation. The coexpression of UGT1A6 had no effect on UGT1A4-catalyzed imipramine N-glucuronide formation but increased the K(m) and V(max) of UGT1A4-catalyzed trifluoperazine N-glucuronide formation. The coexpression of both UGT1A1 and UGT1A4 increased the V(max) values of UGT1A6-catalyzed serotonin and diclofenac O-glucuronide formation. Thus, the effects of the coexpression of other UGT1A isoforms on the kinetics of specific activities were different depending on the UGT1A isoforms and substrates. Native polyacrylamide gel electrophoresis analysis of the double expression systems showed multiple bands at approximately 110 kDa, indicating the existence of heterodimers as well as homodimers of UGTs. In conclusion, we found that human UGT1A1, UGT1A4, and UGT1A6 interact with each other, possibly by heterodimerization, and that their effects on the enzymatic activities are complex depending on the isoforms and substrates.
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Affiliation(s)
- Ryoichi Fujiwara
- Drug Metabolism and Toxicology, Division of Pharmaceutical Sciences, Graduate School of Medical Science, Kanazawa University, Kanazawa 920-1192, Japan
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25
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Patana AS, Kurkela M, Goldman A, Finel M. The human UDP-glucuronosyltransferase: identification of key residues within the nucleotide-sugar binding site. Mol Pharmacol 2007; 72:604-11. [PMID: 17578897 DOI: 10.1124/mol.107.036871] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
UDP-glucuronosyltransferases (UGTs) play important roles in the metabolism, detoxification,and clearance of many different xenobiotics, including drugs and endogenous compounds. Structural information about these membrane-bound enzymes of the endoplasmic reticulum is limited. We do not know the identity or the location of the key residues for catalysis and binding of the aglycone substrate and the cosubstrate UDP-glucuronic acid (UDPGA). One suggestion was that His371 (UGT1A6 numbering) is the "catalytic base" that deprotonates the phenol group. We have now re-examined this hypothesis by analyzing the activities of the corresponding mutants, 6H371A (in UGT1A6) and the 9H369A (in UGT1A9). The K(m) values of mutant 6H371A for scopoletin and UDPGA were higher by 4- and 11-fold, respectively, than in UGT1A6. The K(d) for the enzyme-UDPGA complex, derived from bisubstrate kinetics, was about 9-fold higher in 6H371A than in UGT1A6, indicating severely impaired cosubstrate binding by the mutant. The effect of mutation on V(max) was large in UGT1A6 but variable in UGT1A9, suggesting that His371 does not play the catalytic role previously hypothesized. In both UGTs, the E379A mutation (UGT1A6 numbering) had an effect similar to that of the H371A mutations. A homology model of the putative UDPGA binding region of UGT1A6 was built using distant homologous protein structures from the "GT1 class." The combined results of activity determinations, kinetic analyses, and modeling strongly suggest that His371 and Glu379 are directly involved in UDPGA binding but are not the general acid or general base.
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Affiliation(s)
- Anne-Sisko Patana
- Structural Biology and Biophysics, Institute of Biotechnology, University of Helsinki, Finland
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26
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Fujiwara R, Nakajima M, Yamanaka H, Nakamura A, Katoh M, Ikushiro SI, Sakaki T, Yokoi T. Effects of Coexpression of UGT1A9 on Enzymatic Activities of Human UGT1A Isoforms. Drug Metab Dispos 2007; 35:747-57. [PMID: 17293379 DOI: 10.1124/dmd.106.014191] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We established stable HEK293 cell lines expressing double isoforms, UGT1A1 and UGT1A9, UGT1A4 and UGT1A9, or UGT1A6 and UGT1A9, as well as stable cell lines expressing each single isoform. To analyze the protein-protein interaction between the UGT1As, we investigated the thermal stability and resistance to detergent. UGT1A9 uniquely demonstrated thermal stability, which was enhanced in the presence of UDP-glucuronic acid (>90% of control), and resistance to detergent. Interestingly, UGT1A1, UGT1A4, and UGT1A6 acquired thermal stability and resistance to detergent by the coexpression of UGT1A9. An immunoprecipitation assay revealed that UGT1A6 and UGT1A9 interact in the double expression system. Using the single expression systems, it was confirmed that estradiol 3-O-glucuronide, imipramine N-glucuronide, serotonin O-glucuronide, and propofol O-glucuronide formations are specific for UGT1A1, UGT1A4, UGT1A6, and UGT1A9, respectively. By kinetic analyses, we found that the coexpressed UGT1A9 significantly affected the kinetics of estradiol 3-O-glucuronide formation (decreased Vmax), imipramine N-glucuronide formation (increased Km and Vmax), and serotonin O-glucuronide formation (decreased Vmax) catalyzed by UGT1A1, UGT1A4, and UGT1A6, respectively. On the other hand, the coexpressed UGT1A1 increased Km and decreased the Vmax of the propofol O-glucuronide formation catalyzed by UGT1A9. The coexpressed UGT1A4 and UGT1A6 also increased the Vmax of the propofol O-glucuronide formation by UGT1A9. This is the first study showing that human UGT1A isoforms interact with other isoforms to change the enzymatic characteristics.
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Affiliation(s)
- Ryoichi Fujiwara
- Drug Metabolism and Toxicology, Division of Pharmaceutical Sciences, Graduate School of Medical Science, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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27
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Kurkela M, Patana AS, Mackenzie PI, Court MH, Tate CG, Hirvonen J, Goldman A, Finel M. Interactions with other human UDP-glucuronosyltransferases attenuate the consequences of the Y485D mutation on the activity and substrate affinity of UGT1A6. Pharmacogenet Genomics 2007; 17:115-26. [PMID: 17301691 DOI: 10.1097/fpc.0b013e328011b598] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVES To explore the possible role of hetero-oligomerization among the human UDP-glucuronosyltransferases in attenuating the consequences of the pathological Y486D mutation (UGT1A1 numbering) that often causes hyperbilirubinaemia. Owing to exon sharing in the human UGT1A gene, the equivalent mutation is present in all other UGT1As of the affected individuals. It is unknown, however, if this mutation results in clinical conditions, other than impaired bilirubin conjugation by UGT1A1. METHODS The main experimental approach in this study was to try and form hetero-oligomers of selected UDP-glucuronosyltransferases by coinfecting insect cells with recombinant baculoviruses that encode different human UDP-glucuronosyltransferases and mutants thereof. The infected cells were analysed for both relative expression levels and catalytic activity in each case, the combination of which yielded normalized activity. Kinetic analyses and copurification by affinity chromatography were also performed. RESULTS Coinfections with UGT1A4 increased the normalized scopoletin glucuronidation of 6YD (the Y485D mutant of UGT1A6) much more than it affected 1YD (the Y486D mutant of UGT1A1). Serotonin glucuronidation analyses revealed that coexpression of 6YD with most other human UDP-glucuronosyltransferases significantly increased the normalized activity of this mutant. Using 1-naphthol as the aglycone substrate, the Km of 6YD for the cosubstrate UDP-glucuronic acid was about 50 times higher than in UGT1A6. Yet, coexpression of 6YD with UGT1A4 lowered the Km for UDP-glucuronic acid to the level of UGT1A6. Coexpression also influenced wild-type UGT1A6 and UGT2B7, increasing the normalized activity of UGT1A6, but decreasing it for UGT2B7. CONCLUSION Hetero-oligomerization may play an important role in UDP-glucuronosyltransferases activity.
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Affiliation(s)
- Mika Kurkela
- Drug Discovery and Development Technology Center (DDTC) and Division of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Helsinki, Helsinki, Finland
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28
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Barre L, Fournel-Gigleux S, Finel M, Netter P, Magdalou J, Ouzzine M. Substrate specificity of the human UDP-glucuronosyltransferase UGT2B4 and UGT2B7. Identification of a critical aromatic amino acid residue at position 33. FEBS J 2007; 274:1256-64. [PMID: 17263731 DOI: 10.1111/j.1742-4658.2007.05670.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The human UDP-glucuronosyltransferase (UGT) isoforms UGT2B4 and UGT2B7 play a major role in the detoxification of bile acids, steroids and phenols. These two isoforms present distinct but overlapping substrate specificity, sharing common substrates such as the bile acid hyodeoxycholic acid (HDCA) and catechol-estrogens. Here, we show that in UGT2B4, substitution of phenylalanine 33 by leucine suppressed the activity towards HDCA, and impaired the glucuronidation of several substrates, including 4-hydroxyestrone and 17-epiestriol. On the other hand, the substrate specificity of the mutant UGT2B4F33Y, in which phenylalanine was replaced by tyrosine, as found at position 33 of UGT2B7, was similar to wild-type UGT2B4. In the case of UGT2B7, replacement of tyrosine 33 by leucine strongly reduced the activity towards all the tested substrates, with the exception of 17-epiestriol. In contrast, mutation of tyrosine 33 by phenylalanine exhibited similar or even somewhat higher activities than wild-type UGT2B7. Hence, the results strongly indicated that the presence of an aromatic residue at position 33 is important for the activity and substrate specificity of both UGT2B4 and UGT2B7.
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Affiliation(s)
- Lydia Barre
- UMR 7561 CNRS, Université Henri Poincaré-Nancy I, Faculté de Médecine, F-54505 Vandoeuvre-lès-Nancy, France
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29
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Operaña TN, Tukey RH. Oligomerization of the UDP-glucuronosyltransferase 1A proteins: homo- and heterodimerization analysis by fluorescence resonance energy transfer and co-immunoprecipitation. J Biol Chem 2006; 282:4821-4829. [PMID: 17179145 DOI: 10.1074/jbc.m609417200] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
UDP-glucuronosyltransferases (UGTs) are membrane-bound proteins localized to the endoplasmic reticulum and catalyze the formation of beta-d-glucopyranosiduronic acids (glucuronides) using UDP-glucuronic acid and acceptor substrates such as drugs, steroids, bile acids, xenobiotics, and dietary nutrients. Recent biochemical evidence indicates that the UGT proteins may oligomerize in the membrane, but conclusive evidence is still lacking. In the present study, we have used fluorescence resonance energy transfer (FRET) to study UGT1A oligomerization in live cells. This technique demonstrated that UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, and UGT1A10 self-oligomerize (homodimerize). Heterodimer interactions were also explored, and it was determined that UGT1A1 was capable of binding with UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, and UGT1A10. In addition to the in vivo FRET analysis, UGT1A protein-protein interactions were demonstrated through co-immunoprecipitation experiments. Co-expression of hemagglutinin-tagged and cyan fluorescent protein-tagged UGT1A proteins, followed by immunoprecipitation with anti-hemagglutinin beads, illustrated the potential of each UGT1A protein to homodimerize. Co-immunoprecipitation results also confirmed that UGT1A1 was capable of forming heterodimer complexes with all of the UGT1A proteins, corroborating the FRET results in live cells. These preliminary studies suggest that the UGT1A family of proteins form oligomerized complexes in the membrane, a property that may influence function and substrate selectivity.
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Affiliation(s)
- Theresa N Operaña
- Departments of Chemistry & Biochemistry and Pharmacology, Laboratory of Environmental Toxicology, University of California, San Diego, La Jolla, California 92093
| | - Robert H Tukey
- Departments of Chemistry & Biochemistry and Pharmacology, Laboratory of Environmental Toxicology, University of California, San Diego, La Jolla, California 92093.
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30
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Sten T, Qvisen S, Uutela P, Luukkanen L, Kostiainen R, Finel M. Prominent but Reverse Stereoselectivity in Propranolol Glucuronidation by Human UDP-Glucuronosyltransferases 1A9 and 1A10. Drug Metab Dispos 2006; 34:1488-94. [PMID: 16763014 DOI: 10.1124/dmd.106.010371] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Propranolol is a nonselective beta-adrenergic blocker used as a racemic mixture in the treatment of hypertension, cardiac arrhythmias, and angina pectoris. For study of the stereoselective glucuronidation of this drug, the two propranolol glucuronide diastereomers were biosynthesized, purified, and characterized. A screen of 15 recombinant human UDP-glucuronosyltransferases (UGTs) indicated that only a few isoforms catalyze propranolol glucuronidation. Analysis of UGT2B4 and UGT2B7 revealed no significant stereoselectivity, but these two enzymes differed in glucuronidation kinetics. The glucuronidation kinetics of R-propranolol by UGT2B4 exhibited a sigmoid curve, whereas the glucuronidation of the same substrate by UGT2B7 was inhibited by substrate concentrations above 1 mM. Among the UGTs of subfamily 1A, UGT1A9 and UGT1A10 displayed high and, surprisingly, opposite stereoselectivity in the glucuronidation of propranolol enantiomers. UGT1A9 glucuronidated S-propranolol much faster than R-propranolol, whereas UGT1A10 exhibited the opposite enantiomer preference. Nonetheless, the Km values for the two enantiomers, both for UGT1A9 and for UGT1A10, were in the same range, suggesting similar affinities for the two enantiomers. Unlike UGT1A9, the expression of UGT1A10 is extrahepatic. Hence, the reverse stereoselectivity of these two UGTs may signify specific differences in the glucuronidation of propranolol enantiomers between intestine and liver microsomes. Subsequent experiments confirmed this hypothesis: human liver microsomes glucuronidated S-propranolol faster than R-propranolol, whereas human intestine microsomes glucuronidated S-propranolol faster. These findings suggest a contribution of intestinal UGTs to drug metabolism, at least for UGT1A10 substrates.
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Affiliation(s)
- Taina Sten
- Division of Pharmaceutical Chemistry, University of Helsinki, Finland
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31
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Engtrakul JJ, Foti RS, Strelevitz TJ, Fisher MB. ALTERED AZT (3′-AZIDO-3′-DEOXYTHYMIDINE) GLUCURONIDATION KINETICS IN LIVER MICROSOMES AS AN EXPLANATION FOR UNDERPREDICTION OF IN VIVO CLEARANCE: COMPARISON TO HEPATOCYTES AND EFFECT OF INCUBATION ENVIRONMENT. Drug Metab Dispos 2005; 33:1621-7. [PMID: 16049128 DOI: 10.1124/dmd.105.005058] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Human liver microsomes are a reagent commonly used to predict human hepatic clearance of new chemical entities via phase 1 metabolism. Another common metabolic pathway, glucuronidation, can also be observed in human liver microsomes, although the scalability of this process has not been validated. In fact, several groups have demonstrated that clearance estimated from liver microsomes with UDP-glucuronic acid typically underpredicts the actual in vivo clearance more than 10-fold for compounds that are predominantly glucuronidated. In contrast, clearance predicted using human hepatocytes, for these same compounds, provides a more accurate assessment of in vivo clearance. We sought to characterize the kinetics of glucuronidation of the selective UGT2B7 substrate AZT (3'-azido-3'-deoxythymidine), a selective UGT2B7 substrate, in human liver microsomes (HLMs), recombinant UGT2B7, and human hepatocytes. Apparent Km values in these three preparations were 760, 490, and 87 microM with apparent Vmax values highest in hepatocytes. The IC50 for ibuprofen against AZT glucuronidation, when run at its Km concentration in HLMs and hepatocytes, was 975 and 170 microM respectively. Since incubation conditions have been shown to modulate glucuronidation rates, AZT glucuronidation was performed in various physiological and nonphysiological buffer systems, namely Tris, phosphate, sulfate, carbonate, acetate, human plasma, deproteinized human liver cytosol, and Williams E medium. The data showed that carbonate and Williams E medium, more physiologically relevant buffers, yielded the highest rates of AZT glucuronidation. Km observed in HLM/carbonate was 240 microM closer to that found in hepatocytes, suggesting that matrix differences might cause the kinetic differences observed between liver preparations. Caution should be exercised when extrapolating metabolic lability via glucuronidation or inhibition of UGT enzymes from human liver microsomes, since this system appears to underpredict the degree of lability or inhibition, respectively, due in part to an apparent decrease in substrate affinity.
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Affiliation(s)
- Juntyma J Engtrakul
- Pharmacokinetics, Dynamics, and Metabolism, Pfizer Global Research and Development, Groton, CT 06340, USA
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Luukkanen L, Taskinen J, Kurkela M, Kostiainen R, Hirvonen J, Finel M. KINETIC CHARACTERIZATION OF THE 1A SUBFAMILY OF RECOMBINANT HUMAN UDP-GLUCURONOSYLTRANSFERASES. Drug Metab Dispos 2005; 33:1017-26. [PMID: 15802387 DOI: 10.1124/dmd.105.004093] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The initial glucuronidation rates were determined for eight recombinant human UDP-glucuronosyltransferases (UGTs) of the 1A subfamily, and the bisubstrate kinetics and inhibition patterns were analyzed. At low substrate concentrations, the reactions followed general ternary complex kinetics, whereas at higher concentrations of both substrates, the reactions were mostly characterized by ternary complex kinetics with substrate inhibition. The glucuronidation of entacapone by UGT1A9 was inhibited by 1-naphthol in a competitive fashion, with respect to entacapone, and an uncompetitive fashion, with respect to UDP-glucuronic acid (UDPGA). Its inhibition by UDP, on the other hand, was noncompetitive with respect to entacapone and competitive with respect to UDPGA. These inhibition patterns are compatible with a compulsory ordered bi bi mechanism in which UDPGA is the first-binding substrate. Despite the identical primary structure of the C-terminal halves of the UGT1A isoforms, there were marked differences in the respective K(m) values for UDPGA, ranging from 52 microM for UGT1A6 to 1256 microM for UGT1A8. Relative specificity constants were calculated for the eight UGT1A isoforms with 1-hydroxypyrene, 4-nitrophenol, scopoletin, 4-methylumbelliferone, and entacapone as aglycone substrates. The results demonstrated that seven of the UGT1A isoforms are capable of conjugating phenolic substrates with similar highest k(cat) values, and UGT1A4 has a lower relative turnover rate. The highest specificity constants were obtained for 1-hydroxypyrene, even with UGT1A6, which has been regarded as a specific isoform for small planar phenols. A k(cat) value of 1.9 s(-1) was calculated for the glucuronidation of scopoletin by purified UGT1A9.
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Affiliation(s)
- Leena Luukkanen
- University of Helsinki, Faculty of Pharmacy, Division of Pharmaceutical Chemistry, FIN-00014 Finland.
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Alonen A, Aitio O, Hakala K, Luukkanen L, Finel M, Kostiainen R. BIOSYNTHESIS OF DOBUTAMINE MONOGLUCURONIDES AND GLUCURONIDATION OF DOBUTAMINE BY RECOMBINANT HUMAN UDP-GLUCURONOSYLTRANSFERASES. Drug Metab Dispos 2005; 33:657-63. [PMID: 15689500 DOI: 10.1124/dmd.104.002139] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Selected aspects of dobutamine glucuronidation were studied in detail. There are potentially four sites at which dobutamine can be conjugated to glucuronic acid. Three of the four dobutamine monoglucuronides that can be formed were enzymatically synthesized using pig liver microsomes, isolated, and characterized by tandem mass spectrometry, and (1)H and (13)C NMR spectroscopy. Analysis of dobutamine glucuronidation by liver microsomes from various sources revealed large variability in the ratios of the three regioisomers. Interestingly, catecholic dobutamine meta-O-glucuronide, by far the major product synthesized with human liver microsomes, was only a minor product for rat liver microsomes. Rabbit liver microsomes yielded diglucuronides, in addition to monoglucuronides. Activities of individual recombinant human UDP-glucuronosyltransferases (UGTs) were investigated, and the results suggested that dobutamine glucuronidation in the human liver is mainly carried out by UGTs 2B7 and 1A9. Among the extrahepatic UGTs, the formation of monoglucuronides, mainly catecholic meta-O-glucuronide, by UGTs 1A7 and 1A8 was similar to that by 1A9, whereas UGT1A10 also efficiently catalyzed the formation of catecholic dobutamine para-O-glucuronide.
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Affiliation(s)
- Anna Alonen
- Division of Pharmaceutical Chemistry, Faculty of Pharmacy, University of Helsinki, Finland
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Radominska-Pandya A, Ouzzine M, Fournel-Gigleux S, Magdalou J. Structure of UDP‐Glucuronosyltransferases in Membranes. Methods Enzymol 2005; 400:116-47. [PMID: 16399347 DOI: 10.1016/s0076-6879(05)00008-x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
This chapter presents the most recent experimental approaches to the investigation of UDP-glucuronosyltransferase (UGTs) in membranes. The first topic described is the subcellular localization of UGTs with special emphasis on the association of these proteins with the endoplasmic reticulum (ER). Experimental methods include subfractionation of tissue for microsome preparation, evaluation of the purity of the membrane fraction obtained, and measurement of UGT activity in the presence of detergents. Next, the recently demonstrated formation of UGT homo- and heterodimer formation and its functional relevance is discussed and the appropriate methods used to characterize such interactions are given (radiation inactivation, size exclusion chromatography, immunopurification, cross-linking, two-hybrid system). The structural determinants of UGTs in relation to membrane association, residency, and enzymatic activity are the next topic, supplemented by a description of the appropriate methods, including the design and expression of chimeric proteins, membrane insertion, and subcellular localization by immunofluorescence. Also presented is new information on the structure and function of UGTs obtained by molecular modeling, bioinformatics (sequence alignment), and comparison with selected crystallized glycosyltransferases. Finally, we discuss the important, and still not fully developed, issue of UGT active site architecture and organization within the ER. This is addressed from two perspectives: (1) chemical modification of UGT active sites by amino acid-specific probes and (2) photoaffinity labeling of UGTs. The detailed synthesis of a photoaffinity probe for an aglycon-binding site is provided and the use of this probe and direct photoaffinity labeling with retinoids is discussed. The application of proteomics techniques, including proteolytic digestion and protein sequencing by liquid chromatography/tandem mass spectrometry and matrix-assisted laser desorption ionization/time of flight, to the identification of crucial amino acids of the active sites, and subsequent site-directed mutagenesis of identified amino acids, is discussed in detail.
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Affiliation(s)
- Anna Radominska-Pandya
- Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, USA
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