Acetaminophen metabolic enzyme

Acetaminophen metabolic enzymes refer to a set of hepatic proteins that orchestrate the biotransformation of acetaminophen (APAP), determining its therapeutic efficacy and potential for toxicity (PharmGKB, 2017; PMC, 2019). The predominant metabolic routes involve phase II conjugation by UDP-glucuronosyltransferases (UGTs) and sulfotransferases (SULTs), which convert APAP into water-soluble, non-toxic metabolites for urinary excretion (ClinPGx, 2021; PubMed, 1993). A critical minor pathway is mediated by Cytochrome P450 enzymes, primarily Cytochrome P450 2E1 (CYP2E1), which bioactivate APAP into the highly reactive electrophile N-acetyl-p-benzoquinone imine (NAPQI) (StatPearls, 2023; NIH, 2018). At therapeutic doses, NAPQI is efficiently detoxified by glutathione S-transferases (GSTs) using reduced glutathione (GSH) (Wikipedia, 2025; NIH, 2021). However, in toxic overdoses, GSH stores are depleted, allowing NAPQI to form covalent adducts with mitochondrial proteins, initiating a cascade of oxidative stress and hepatocyte necrosis (NIH, 2018; PMC, 2019). This metabolic system is the focus of clinical monitoring for drug-induced liver injury and is the primary target for the antidote N-acetylcysteine, which serves to replenish the cellular glutathione pool (NIH, 2021; PharmGKB, 2017).

Other names

Liver enzymes for acetaminophen metabolismAcetaminophen metabolic enzymesAPAP metabolic enzymesParacetamol metabolic enzymesAcetaminophen metabolic pathwayCytochrome P450 enzymes involved in APAP metabolism

Metabolism of acetaminophen into stable glucuronide and sulfate conjugates, and oxidative bioactivation into the toxic metabolite NAPQI, which is subsequently detoxified by glutathione conjugation.