Purity ≥95% by RP-HPLC and SDS-PAGE. Chromatographically purified. Alanine aminotransferase (ALT, GPT, Gutamate pyruvate transaminanse), catalyzes the transamination reaction. ALT requires pyridoxal-5-phosphate (PLP) as prosthetic group. ALT was previously known as serum glutamic pyruvic transaminase (SGPT). ALT is a cytoplasmic enzyme that catalyzes the transamination of alpha-ketoglutarate and L-alanine, forming glutamate and pyruvate. ALT is found in liver, kidney, brain and heart , as two isoforms: cytosolic ALT and mitochondrial ALT. These enzymes function in cellular nitrogen metabolism and also liver gluconeogenesis. The highest activities of ALT are found in hepatocytes and striated (skeletal and cardiac) muscle cells. Therefore, increased serum ALT activity can accompany hepatocellular injury or necrosis of striated muscle. With cell injury or death, ALT (a leakage enzyme) escapes from the cytosol. Determination of ALT activity is a relatively sensitive indicator of hepatic