GAD

Glutamic acid decarboxylase (GAD) is an enzyme that plays a key role in the production of gamma-aminobutyric acid (GABA), a neurotransmitter that regulates the activity of nerve cells in the brain and other parts of the body. GAD converts glutamate, an excitatory neurotransmitter, into GABA, an inhibitory neurotransmitter, by removing a carboxyl group from glutamate. GAD requires pyridoxal phosphate (PLP), a form of vitamin B6, as a cofactor for this reaction. GAD exists in two isoforms, GAD65 and GAD67, which are encoded by different genes and have different functions and locations in the body. GAD65 is mainly found in the pancreas, where it helps to regulate insulin secretion, and in some neurons, where it responds to synaptic activity. GAD67 is widely distributed in the brain, where it maintains a steady supply of GABA for synaptic transmission. GAD is involved in several diseases, such as type 1 diabetes, stiff person syndrome, epilepsy, and some neurological disorders. These diseases are associated with the presence of autoantibodies that target GAD and impair its function or destroy its producing cells.