PT  - JOURNAL ARTICLE
AU  - Mithat Gunduz
AU  - Upendra A. Argikar
AU  - Daniel Baeschlin
AU  - Suzie Ferreira
AU  - Vinayak Hosagrahara
AU  - Shawn Harriman
TI  - Identification of a Novel <em>N</em>-Carbamoyl Glucuronide: In Vitro, In Vivo, and Mechanistic Studies
AID  - 10.1124/dmd.109.030650
DP  - 2010 Mar 01
TA  - Drug Metabolism and Disposition
PG  - 361--367
VI  - 38
IP  - 3
4099  - http://dmd.aspetjournals.org/content/38/3/361.short
4100  - http://dmd.aspetjournals.org/content/38/3/361.full
SO  - Drug Metab Dispos2010 Mar 01; 38
AB  - 1-[4-Aminomethyl-4-(3-chlorophenyl)-cyclohexyl]-tetrahydro-pyrimidin- 2-one, 1, was developed as an inhibitor of dipeptidyl peptidase-4 enzyme. Biotransformation studies with 1 revealed the presence of an N-carbamoyl glucuronide metabolite (M1) in rat bile and urine. N-Carbamoyl glucuronides are rarely observed, and little is understood regarding the mechanism of N-carbamoyl glucuronidation. The objectives of the current investigation were to elucidate the structure of the novel N-carbamoyl glucuronide, to investigate the mechanism of N-carbamoyl glucuronide formation in vitro using stable labeled CO2, UDP glucuronosyltransferase (UGT) reaction phenotyping, and to assess whether M1 was formed to the same extent in vitro across species—mouse, rat, hamster, dog, monkey, and human. Structure elucidation was performed on a mass spectrometer with accurate mass measurement and MSn capabilities. 13C-labeled carbon dioxide was used for identification of the mechanism of N-carbamoyl glucuronidation. Mechanistic studies with 13C-labeled CO2 in rat liver microsomes revealed that CO2 from the bicarbonate buffer (in equilibrium with exogenous CO2) may be responsible for the formation of M1. M1 was formed in vitro in liver microsomes from multiple species, mainly rat and hamster, followed by similar formation in dog, monkey, mouse, and human. M1 could be detected in UGT1A1, UGT1A3, and UGT2B7 Supersomes in a CO2-rich environment. In conclusion, our study demonstrates that formation of M1 was observed in microsomal incubations across various species and strongly suggests incorporation of CO2 from the bicarbonate buffer, in equilibrium with exogenous CO2, into the carbamoyl moiety of the formed N-carbamoyl glucuronide. Copyright © 2010 by The American Society for Pharmacology and Experimental Therapeutics