Glucuronidation of Tobacco-Specific Nitrosamines by UGT2B10

Abstract

ABSTRACT:4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is an important tobacco-specific nitrosamine (TSNA) in the etiology of tobacco-related cancers, and N-glucuronidation is an important mechanism of NNAL detoxification. In the present study, an analysis of the UDP-glucuronosyltransferases (UGTs) responsible for the Nglucuronidation of the TSNAs N-nitrosonornicotine, N-nitrosoanabasine, and N-nitrosoanatabine was performed. Using human embryonic kidney 293 cells overexpressing UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B4, UGT2B7, UGT2B10, UGT2B11, UGT2B15, and UGT2B17, only UGT1A4 and UGT2B10 exhibited N-glucuronidating activity against these TSNAs. The K M s for UGT2B10 were 15 to 22-fold lower than those of UGT1A4 against the three TSNAs and were similar to those observed for microsomes prepared from human liver specimens. The overall activity of UGT2B10 was 3.6 to 27-fold higher than UGT1A4 against the three TSNAs as determined by V max /K M after normalization by levels of UGT2B10 versus UGT1A4 mRNA. Similarly high levels of activity were also observed for UGT2B10 against a fourth TSNA, NNAL, exhibiting a 6.3-fold lower K M and 3-fold higher normalized V max /K M than that observed for UGT1A4. Real-time polymerase chain reaction analysis showed that UGT2B10 was expressed at a level that, on average, was 26% higher than that observed for UGT1A4 in a screening of normal liver tissue specimens from 20 individual subjects. These data suggest that UGT2B10 is likely the most active UGT isoform in human liver for the N-glucuronidation of TSNAs.

Influence of N-Terminal Domain Histidine and Proline Residues on the Substrate Selectivities of Human UDP-Glucuronosyltransferase 1A1, 1A6, 1A9, 2B7, and 2B10

“…More recently, UGT2B10 has been shown to glucuronidate certain tertiary amines, including cotinine, nicotine, and tobacco-specific nitrosamines, but activities are relatively low (Chen et al, 2007(Chen et al, , 2008Kaivosaari et al, 2007). The UGT2B10(L34H) mutant was found here to glucuronidate 4MU and 1NP but not cotinine.…”

Human UDP-Glucuronosyltransferase (UGT) 2B10 in DrugN-Glucuronidation: Substrate Screening and Comparison with UGT1A3 and UGT1A4

“…A breakthrough occurred in 2007 with the findings from two different laboratories that UGT2B10 catalyzes the N-glucuronidation of nicotine and cotinine (Chen et al, 2007;Kaivosaari et al, 2007). It was later reported that UGT2B10 also catalyzes the N-glucuronidation of nitrosamines (Chen et al, 2008) and R-medetomidine (Kaivosaari et al, 2008). These UGT2B10 substrates are also glucuronidated by UGT1A4, but at much lower affinity.…”

UGT2B Gene Expression Analysis in Multiple Tobacco Carcinogen-Targeted Tissues

“…at ASPET Journals on May 11, 2018 dmd.aspetjournals.org UGT2B10 was shown to be the primary enzyme responsible for the formation of NNAL-N-gluc (Chen et al, 2008b). Relative to other UGT2B genes, UGT2B10 mRNA was expressed at the second-highest level of all UGT2B genes in tongue tissue and could play an important role in tobacco carcinogen detoxification at this site.…”

“…The UGTs also play an important role in the metabolism and detoxification of multiple tobacco carcinogens, including tobacco-specific nitrosamines like 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and its major metabolite 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) (Ren et al, 2000;Wiener et al, 2004a;Chen et al, 2008b), and polycyclic aromatic hydrocarbons like benzo(a)pyrene [B(a)P]-7,8-diol and dibenzo(a,l)pyrene-11,12-diol [DB(a,l)P] (Fang et al, 2002;Olson et al, 2011). The UGTs primarily consist of two large subfamilies, the UGT1As and the UGT2Bs.…”