Aspartate aminotransferase is a pyridoxal phosphate-dependent enzyme which exists in cytoplasmic and mitochondrial forms, aspartate aminotransferase and GOT2, respectively. GOT plays a role in amino acid metabolism and the urea and tricarboxylic acid cycles. The two enzymes are homodimeric and show close homology. There is a rare in-frame deletion in aspartate aminotransferase gene, which inactivates cytosolic aspartate aminotransferase(cAST) enzyme in the Old Order Amish. This may help to understand structure and function of the enzyme and would be useful for predicting serum aspartate AST levels.