Which in vitro assay measures metabolic processing by liver enzymes?

• A. In vitro metabolism by CYP enzymes
• B. Genotoxicity
• C. Cytotoxicity
• D. Receptor-ligand binding assays

Answer: (A)

Understanding how a compound is transformed by liver enzymes is the key idea. In vitro metabolism assays use liver-derived enzymes, especially cytochrome P450 enzymes, to simulate metabolic processing in the body. By providing NADPH, these systems (like liver microsomes or hepatocytes) measure how quickly the parent compound is metabolized and what metabolites are formed, giving insight into metabolic stability and predicted in vivo clearance. This directly assesses metabolic processing by liver enzymes. The other types of assays focus on different toxicology aspects: genotoxicity looks at DNA damage, cytotoxicity assesses cell viability, and receptor-ligand binding evaluates how a molecule binds to a receptor rather than how it is chemically transformed by enzymes. So, measuring in vitro metabolism by CYP enzymes is the best match.