Serum alanine aminotransferase, an enzyme that transfers amino acids from the amino group to the keto group of keto acids, is found mainly in the cytoplasm of liver cells. In acute viral hepatitis, alanine aminotransferase may be significantly elevated. In addition, in chronic hepatitis or fatty liver, alanine aminotransferase may also be mildly elevated. When cirrhosis or liver cancer is present, alanine aminotransferase may also be mildly elevated or normal. In other diseases, such as infectious mononucleosis, alanine aminotransferase may also be mildly elevated.