Liver enzymes are proteins that accelerate chemical reactions in the liver. Commonly measured liver enzymes include Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST), Alkaline Phosphatase (ALP), and Gamma-Glutamyl Transferase (GGT). These enzymes are crucial indicators of liver function, and their levels can help diagnose liver diseases or monitor the efficacy of treatments.