RT Journal Article SR Electronic T1 Formation of the Quaternary Ammonium-Linked Glucuronide of Nicotine in Human Liver Microsomes: Identification and Stereoselectivity in the Kinetics JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 1525 OP 1528 VO 29 IS 12 A1 Ghosheh, Omar A1 Vashishtha, Sarvesh C. A1 Hawes, Edward M. YR 2001 UL http://dmd.aspetjournals.org/content/29/12/1525.abstract AB The formation of the N1-glucuronide metabolite of each nicotine enantiomer was studied in pooled human liver microsomes (n = 6). The metabolite formed from natural S(−)-nicotine was identified by comparison of the high-pressure liquid chromatography (HPLC) retention time and positive ion electrospray ionization-mass spectral characteristics with a synthetic reference standard. A radiometric HPLC method was used to quantify the metabolite. The specificity of the assay method was demonstrated by experiments in which β-glucuronidase treatment of incubated assay samples resulted in elimination of the peak due to theN1-glucuronide metabolite. The glucuronides ofS(−)- and R(+)-nicotine were formed by one-enzyme kinetics, with Km values of 0.11 and 0.23 mM and Vmax values of 132 and 70 pmol/min/mg of protein, respectively. There is marked stereoselectivity in the apparent intrinsic clearance values (Vmax/Km) in that the value for S(−)-nicotine is 4 times greater than for the R(+)-isomer (1.2 versus 0.31 μl/min/mg of protein). The American Society for Pharmacology and Experimental Therapeutics