Inhibition of aminotransferase enzyme systems by gabaculine

Addition of gabaculine to brain and liver extracts caused great inhibition of GABA-T activity, a much lesser but still significant inhibition of ALA-T activity, and very little inhibition of ASP-T activity. In contrast, intramuscular administration of gabaculine to mice resulted in considerable inhibition of all three enzyme activities in liver, the order of sensitivity being ALA-T greater than GABA-T greater than ASP-T. The effect of the administered gabaculine on the brain enzyme activities was more along the lines seen in the in vitro experiments but, even here, the relative sensitivities of GABA-T and ALA-T to the inhibition were much more similar than might have been predicted from the in vitro experiments.