RT Journal Article SR Electronic T1 Nicotinamide N-Oxidation by CYP2E1 in Human Liver Microsomes JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 550 OP 553 DO 10.1124/dmd.112.049734 VO 41 IS 3 A1 Real, Alexander Michael A1 Hong, Shangyu A1 Pissios, Pavlos YR 2013 UL http://dmd.aspetjournals.org/content/41/3/550.abstract AB Excess nicotinamide, a form of vitamin B3, is metabolized through two enzymatic systems and eventually excreted from the body. The first system starts with the methylation of nicotinamide by nicotinamide N-methyltransferase, which can subsequently be oxidized by aldehyde oxidase. The second enzymatic system oxidizes nicotinamide to nicotinamide N-oxide. It is located in the endoplasmic reticulum of hepatocytes but the precise enzyme is unknown. We have used human liver microsomes in combination with selective cytochrome P450 inhibitors, specific substrates, and antibodies to identify CYP2E1 as the main activity producing nicotinamide N-oxide. Our results suggest the potential use of nicotinamide N-oxide as a biomarker of CYP2E1 activity from urine or blood samples.