Aspartate aminotransferase is an enzyme found in heart, liver, skeletal muscle, pancreas, kidney and red blood cells. It is an aminotransferase, transferring an amino group to ketoacids. It requires pyridoxal-5-phosphate as a coenzyme. Increased plasma activity is the result of leakage of enzyme from tissues as a result of cellular damage: it is found predominantly in the cytoplasm and mitochondria.