Aminotransferase: An enzyme that catalyzes the transfer of an amino group from a donor molecule to a recipient molecule. The donor molecule is usually an amino acid while the recipient (acceptor) molecule is usually an alpha-2 keto acid. An aminotransferase is also called a transaminase. Two of the better known enzymes in this class are serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT). Both of these transaminases (SGOT and SGPT) are normally found primarily in cells in the liver and heart, are released into the bloodstream as the result of liver or heart damage, and so are used as liver and heart tests.