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

Abstract

Gabaculine, 5-amino-1,3-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 Ki for D-3-aminoisobutyrate-pyruvate aminotransferase was 8.3 x 10(-6) M, and the Kcat for its turnover was 0.31 min-1 at 25 degrees C. beta-Alanine protected the enzyme from inactivation by gabaculine, but GABA did so to much a lesser extent.