NAD(+)-dependent formation ofγ-aminobutyrate (GABA) from glutamate.

Mitochondria and nuclei of various tissues, including brain and liver, are capable of producingγ-aminobutyrate (GABA) fromL-glutamate, but poorly, if at all, fromD-glutamate. The amino nitrogen of glutamate is found in the reaction product. The enzymes responsible for GABA formation were solubilized from crude liver cell nuclei by Triton X-100. The reaction is NAD(+) dependent Oxygen, FMN, Mg(2+), and pyridoxalphosphate enhanced GABA formation. NADP(+), coenzyme A, ornithine, 2-oxoglutarate, and aminooxyacetic acid, among others, inhibited the formation of GABA. On the basis of the available information the reaction sequence, is formulated tentatively as follows: