A Kinetic Analysis of g-Aminobutyrate Aminotransferase in Presence and Absence of Inhibitors

The kinetics of the reaction catalyzed by γ-aminobutyric acid transaminase (GABA-T) is studied both in the absence and in the presence two inhibitors: n-dipropylacetate (n-DPA) and 4-amino-2-azide-butyric acid (GABA azide). A novel kinetic model is proposed, that is based on an experimentally derived rate equation, which describes the kinetics of the transamination process accounting for the competitive inhibition of the ketoacid and of the added inhibitor (n-DPA, GABA azide). The consequence of the ketoacid inhibition on the primary and secondary double reciprocal plots of the initial velocity against the substrates concentration is examined. The kinetic parameters which describe the rate of the transamination reaction are derived and compared with data reported in the literature. The higher inhibition power of GABA azide with respect to n-DPA is also assessed and discussed.