@article {Ghosheh991, author = {Omar Ghosheh and Edward M. Hawes}, title = { N-Glucuronidation of Nicotine and Cotinine in Human: Formation of Cotinine Glucuronide in Liver Microsomes and Lack of Catalysis by 10 Examined UDP-Glucuronosyltransferases}, volume = {30}, number = {9}, pages = {991--996}, year = {2002}, doi = {10.1124/dmd.30.9.991}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, abstract = {Two predominant human glucuronide metabolites of nicotine result from pyridine nitrogen atom conjugation. The present objectives included determination of the kinetics of formation ofS(-)-cotinine N1-glucuronide in pooled human liver microsomes and investigation of the UDP-glucuronosyltransferases (UGTs) involved inN-glucuronidation of nicotine isomers andS(-)-cotinine by use of recombinant enzymes (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B7, and UGT2B15). Quantification was by radiochemical high-performance liquid chromatography with use of radiolabeled substrates.S(-)-Cotinine N1-glucuronide formation in human liver microsomes was proven by comparing the chromatographic behaviors and electrospray ionization-mass spectral characteristics of the metabolite with a synthetic reference standard. This glucuronide was formed by one-enzyme kinetics with Kmand Vmax values of 5.4 mM and 696 pmol/min/mg, respectively, and the apparent intrinsic clearance value (Vmax/Km) was 9-fold less than that previously determined forS(-)-nicotine N1-glucuronide (0.13 versus 1.2 μl/min/mg) using the same pooled microsomes. This comparison of values is consistent with the observation that on smoking cigarettes, although the average S(-)-cotinine plasma levels usually far exceed S(-)-nicotine levels, the urinary recovery of S(-)-cotinineN1-glucuronide only averages 3-fold greater than forS(-)-nicotine N1-glucuronide. None of the UGTs examined catalyzed the N-glucuronidation ofS(-)-nicotine, R(+)-nicotine, andS(-)-cotinine, including UGT1A3 and UGT1A4, the only isoforms known to catalyze many substrates at a tertiary amine. Also, neither S(-)-nicotine or S(-)-cotinine affected enzyme inhibition of trifluoperazine, a UGT1A4 substrate. It would appear that the same, as yet unexamined, UGT catalyzes theN-glucuronidation of both cotinine and nicotine. The American Society for Pharmacology and Experimental Therapeutics}, issn = {0090-9556}, URL = {https://dmd.aspetjournals.org/content/30/9/991}, eprint = {https://dmd.aspetjournals.org/content/30/9/991.full.pdf}, journal = {Drug Metabolism and Disposition} }