Glutamic acid decarboxylase

Glutamic acid decarboxylase (GAD) is an enzyme that catalyzes the decarboxylation of glutamate to gamma-aminobutyric acid (GABA) and CO2. GAD uses PLP as a cofactor. The reaction proceeds as follows:

L-glutamate + PLP ↔ CO2 + GABA + PMP

There are two isoforms in humans: GAD1 and GAD2. GAD1 is predominantly expressed in the brain, where GABA is used. GAD2 is more widely distributed.

Function

GAD catalyzes the production of GABA, an inhibitory neurotransmitter in the central nervous system. This role can be seen in patients with stiff person syndrome, a neurologic disorder characterized by stiffness and functional impairment of skeletal muscles. Patients with this syndrome often have high levels of GAD antibodies, suggesting an autoimmune component to the disease.

Clinical significance

GAD is a target of autoantibodies in patients with type 1 diabetes mellitus. Less commonly, antibodies against GAD can be found in patients with other autoimmune neurological disorders such as stiff person syndrome, cerebellar ataxia, and limbic encephalitis.

See also

• Gamma-Aminobutyric acid
• Decarboxylation
• Enzyme
• Type 1 diabetes mellitus
• Stiff person syndrome
• Cerebellar ataxia
• Limbic encephalitis

References

Glutamic acid decarboxylase Resources
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