1. Cytoplasmic aspartate aminotransferase was isolated and purified from human heart with a final specific activity of 236 units/mg of protein.
2. Three distinct peaks of aspartate aminotransferase activity were detected by isoelectric focusing with isoelectric points of 5.46, 5.60 and 5.71. Two minor subforms were also noted as shoulder patterns with pI 5.2 and 5.8.
3. These electrophoretic characteristics are similar to previous findings of multiple molecular forms detected in human liver and erythrocytes.