What enzyme in the liver is primarily responsible for metabolizing alcohol?

The enzyme in the liver primarily responsible for metabolizing alcohol is alcohol dehydrogenase.

In liver cells, alcohol dehydrogenase (ADH) begins ethanol breakdown by converting it into acetaldehyde, a toxic compound that contributes to hangover symptoms. The reaction uses NAD+ as a cofactor and takes place mainly in the cytosol of hepatocytes.

Acetaldehyde is then converted into acetate chiefly by aldehyde dehydrogenase, especially ALDH2. That makes aldehyde dehydrogenase essential to the second stage, but not the enzyme that starts the main pathway. Catalase can metabolize small amounts of alcohol, while cytochrome P450 2E1 becomes more important with chronic drinking or high alcohol concentrations.

Individual differences in ADH and ALDH enzymes help explain why people experience alcohol differently. A buildup of acetaldehyde, often linked to reduced ALDH2 activity, can cause facial flushing, nausea and rapid heartbeat.