GAD2 also known as GAD65 is one of several forms of glutamic acid decarboxylase, identified as a major autoantigen in insulin-dependent diabetes. GAD2 plays a crucial role in the synthesis of gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the brain, by catalyzing the conversion of L-glutamic acid to GABA. This process is vital for maintaining the balance of excitatory and inhibitory signals in the nervous system, which is essential for proper neuronal function and preventing excitotoxicity. GAD2 is specifically localized to synaptic vesicle membranes in nerve terminals, allowing for rapid GABA production in response to increased neuronal activity, while GAD1, the other isoform, is distributed throughout the cell and maintains basal GABA levels. The transient activation of GAD2 during heightened neurotransmission underscores its importance in modulating synaptic activity, and loss of GAD2 can lead to significant impairments in GABAergic signaling, highlighting its critical role in neurophysiology.