Irreversible inhibition of D-3-aminoisobutyrate-pyruvate aminotransferase by gabaculine

Gabaculine, 5-amino-l,3-cyclohexadienylcarboxylate, is an analogue of GABA and a potent irreversible inhibitor of GABA aminotransferase. However, D-3-aminoisobutyrate-pyruvate aminotransferase for which GABA was neither a substrate nor an inhibitor was also inactivated by gabaculine. The K i for D-3-aminoisobutyrate-pyruvate aminotransferase was 8.3 × 10 −6 M, and the K cat fot its turnover was 0.31 min −1 at 25°C. β-Alanine protected the enzyme from inactivation by gabaculine, but GABA did so to much a lesser extent.