AMIDE <i>N</i>-GLUCURONIDATION OF MAXIPOST CATALYZED BY UDP-GLUCURONOSYLTRANSFERASE 2B7 IN HUMANS

Zhang, Donglu; Zhao, Weiping; Roongta, Vikram; Mitroka, James; Klunk, Lewis J.; Zhu, Mingshe

doi:10.1124/dmd.32.5.545

Cited by 22 publications

(15 citation statements)

References 29 publications

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“…Only recently has N-glucuronidation by another UGT (UGT2B7) been reported, in the glucuronidation of the secondary amine of an indole-2-one group (Zhang et al, 2004). Here, we report the first evidence that a UGT other than UGT1A3/1A4 can glucuronidate a primary amine; in addition UGT2B7 is the first isoform to be shown to glucuronidate the carbamoyl group.…”

Section: Discussionmentioning

confidence: 66%

N-Glucuronidation of Carbamazepine in Human Tissues Is Mediated by UGT2B7

Staines¹,

Coughtrie²,

Burchell³

2004

J Pharmacol Exp Ther

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Carbamazepine (CBZ) is one of the most widely prescribed anticonvulsants despite a high incidence of idiosyncratic side effects. Metabolism of CBZ is complex, and of the more than 30 metabolites identified, one of the most abundant is CBZ Nglucuronide. To date the uridine diphosphate glucuronosyltransferase (UGT) isoform responsible for the N-glucuronidation of CBZ has not been identified. We have developed a sensitive liquid chromatography/mass spectrometry assay to quantify CBZ glucuronidation, and we report that CBZ is specifically glucuronidated by human UGT2B7. Kinetics of CBZ glucuronidation in human liver, kidney, and intestine microsomes were consistent with those of recombinant UGT2B7, which displayed a K m value of 214 M and V max value of 0.79 pmol/mg/min. In addition to revealing the isoform responsible for CBZ glucuronidation, this is the first example of primary amine glucuronidation by UGT2B7.Carbamazepine (5H-dibenzo[b,f]azepine-5-carboxamide) is one of the most widely prescribed anticonvulsants and is used to treat a variety of conditions from epilepsy to muscle spasm and trigeminal neuralgia. However its use is associated with a number of idiosyncratic adverse side effects, including skin rash, blood disorders, and hepatitis in onethird to one-half of patients (Ju and Uetrecht 1999). These adverse side effects have been associated with the formation of CBZ metabolites (Shear and Spielberg 1988;Riley et al., 1989); therefore, the study of all CBZ metabolites has important clinical implications.The metabolism of CBZ is complex and has been widely studied in human and in animal models (Madden et al., 1996;Maggs et al., 1997) with over 30 metabolites (Lertratanangkoon and Horning, 1982) identified. The major metabolites are the 10,11-epoxide and its hydrolytic trans-dihydrodiol product. Glucuronidation is also an important detoxification pathway because the CBZ N-glucuronide and glucuronides of the hydroxylated metabolites are significant urinary metabolites; however, to date no glucuronide metabolite has been implicated in the incidence of side effects. Epoxide hydrolase has been the focus of most attention as a potential source of toxic metabolites; however, the available data do not support a major role for this enzyme in causing side effects (Pirmohamed et al., 1992;Green et al., 1995b). One minor metabolite, 2-hydroxy-CBZ, formed through loss of the carboxamide, could be metabolized to an iminoquinone, which due to its potential chemical reactivity might be the metabolite responsible for the idiosyncratic reactions, although this has not been shown to date (Ju and Uetrecht, 1999). In addition CBZ is also a well known enzyme inducer up-regulating cytochrome P450 (Luo et al., 2002) and UGT activity/expression (Tanaka, 1999) Carbamazepine is metabolized to an N-glucuronide (Bauer et al., 1976); in addition, glucuronide metabolites have been demonstrated for all 13 of the hydroxylated metabolites of CBZ (Maggs et al., 1997). Formation of N-glucuronides has been principally studied in nonro...

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Section: Discussionmentioning

confidence: 66%

N-Glucuronidation of Carbamazepine in Human Tissues Is Mediated by UGT2B7

Staines¹,

Coughtrie²,

Burchell³

2004

J Pharmacol Exp Ther

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“…This contrasts with several other enzymes, such as UGT1A3 and UGT2B7, that can catalyze the N-glucuronidation of certain aglycones in addition to other glucuronidation reactions (Green and Tephly, 1998;Zenser et al, 2002;Zhang et al, 2004;Borlak et al, 2006;Xu et al, 2006). This difference in function could be reflected by the primary structure of these enzymes, and an inspection of the amino acid sequences of all the human UGTs has indeed revealed an interesting observation.…”

Section: Discussionmentioning

confidence: 80%

“…Our newly developed analytical method was applied to the determination of nicotine and cotinine glucuronidation rates by UGT1A4 and UGT1A9, enzymes reported previously to catalyze nicotine glucuronidation (Kuehl and Murphy, 2003), and by UGT2B7, an enzyme that is involved in the glucuronidation of many structurally diverse xenobiotics including N-glucuronidation reactions (Zhang et al, 2004;Xu et al, 2006). It is noteworthy that the activity of UGT2B10 was also determined because our preliminary studies with this enzyme showed efficient N-glucuronidation of certain other compounds (Kaivosaari S, Koskinen M, and Finel M, manuscript in preparation).…”

Section: Resultsmentioning

confidence: 99%

Nicotine Glucuronidation and the Human UDP-Glucuronosyltransferase UGT2B10

Kaivosaari¹,

Toivonen²,

Hesse³

et al. 2007

Mol Pharmacol

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Nicotine biotransformation affects the smoking habits of addicted individuals and therefore their health risk. Using an improved analytical method, we have discovered that the human UDP-glucuronosyltransferase (UGT) 2B10, a liver enzyme previously unknown to conjugate nicotine or exhibit considerable activity toward any compound, plays a major role in nicotine inactivation by direct conjugation with glucuronic acid at the aromatic nitrogen atom. The K m value of recombinant UGT2B10 for nicotine (0.29 mM) was similar to that determined for human liver microsomes (0.33 mM), whereas the K m value of UGT1A4 for nicotine was almost 10-fold greater (2.4 mM). UGT2B10 was also more active than UGT1A4 in N-glucuronidation of cotinine (oxidative nicotine metabolite), whereas UGT2B7 exhibited only low nicotine glucuronidation activity and was essentially inactive toward cotinine. UGT1A9 did not glucuronidate nicotine or cotinine. Quantitative reverse transcription-polymerase chain reaction showed that UGT2B10 mRNA was exclusively expressed in human liver, whereas UGTs 1A4 and 2B7 were expressed at comparable, although somewhat lower, levels in liver and several other extrahepatic tissues, including kidney and intestine. These findings for UGT2B10 (but not for UGT1A4 and UGT2B7) were mirrored by human tissue activities because nicotine and cotinine glucuronidation rates in intestine microsomes were less than 0.1% that of human liver microsomes. These novel findings solve two seemingly separate questions: which UGT is primarily responsible for nicotine glucuronidation in human liver, and what conjugation reactions are catalyzed by UGT2B10.Nicotine is not carcinogenic by itself and might even have some beneficial therapeutic effects in some neurological diseases. Nonetheless, it is the major perpetrator of tobaccorelated diseases because nicotine addiction drives smokers to pursue the habit despite the known health hazards. Nicotine concentration in the blood increases sharply during cigarette smoking and then decreases rapidly because of metabolism and clearance, driving the addicted individual to reach for another cigarette. Hence, better understanding of nicotine metabolism can assist the development of treatments to reduce the health risks associated with nicotine addiction.Cytochrome P450 monooxygenase 2A6 (CYP2A6) catalyzes nicotine oxygenation and plays an important role in nicotine metabolism (Hukkanen et al., 2005;Nakajima and Yokoi, 2005). However, there is more to nicotine metabolism than CYP2A6 because both nicotine and its primary oxidation metabolite, cotinine, undergo direct N-glucuronidation at the aromatic nitrogen (Fig.

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“…5. In the presence of known UGT2B4 and/or UGT2B7 substrates, HDCA (a UGT2B4 and UGT2B7 substrate) (Barre et al, 2007), fluconazole (a UGT2B7 substrate) (Uchaipichat et al, 2006b), and MaxiPost (a UGT2B7 substrate) (Zhang et al, 2004), the formation of M6 was substantially inhibited (Ͼ57%) in incubations with HLM and expressed UGT2B4 and UGT2B7. The inhibitors of other UGT enzymes, namely bilirubin …”

Section: Incubations Of [mentioning

confidence: 99%

“…BMS-690514, at a concentration of 200 M, was incubated in triplicate with HLM (1 mg/ml), expressed UGT2B4 (0.5 mg/ml), or expressed UGT2B7 (0.5 mg/ml) with 2 mM UDPGA, 10 mM MgCl 2 , 50 g/ml alamethicin, and competitive UGT chemical inhibitors in 0.1 M Tris-HCl buffer (pH 7.5), total reaction volume 0.2 ml. The chemical inhibitors of UGT enzymes evaluated in this study were bilirubin (20 M) for UGT1A1 (Court, 2005), HDCA (600 M) for UGT2B4/7 (Barre et al, 2007), fluconazole (4 mM) for UGT2B7 (Uchaipichat et al, 2006b), hecogenin (100 M) for UGT1A4 (Uchaipichat et al, 2006a), propofol (100 M) for UGT1A9 (Yamanaka et al, 2005), BMS-204352 (100 M; MaxiPost) for UGT2B7 (Zhang et al, 2004), and serotonin (20 mM) for UGT1A6 (Krishnaswamy et al, 2003). The inhibitors at the selected concentrations used here were shown to have inhibitory activity toward the individual UGTs according to the literature citations listed above.…”

Section: Incubations With Hlm and Expressed Ugt Enzymes Fortified Witmentioning

confidence: 99%