Alanine aminotransferase (ALT) is a cytoplasmic enzyme in liver, present in a higher concentration here than in other tissues so it is considered more specific for liver damage.
Aminotransferases are most useful in the diagnosis (e.g. early stages of viral hepatitis) and monitoring of hepatocellular disease, but can also be very high in acute cholestatic disease (especially choledocholithiasis). Marked elevations may also be seen in acute profound hypotension and acute cardiac failure.