Glutamate decarboxylase

In biochemistry, glutamate decarboxylase (GAD) is an enzyme that is "pyridoxal-phosphate protein that catalyzes the alpha-decarboxylation of L-glutamic acid to form gamma-aminobutyric acid and carbon dioxide. The enzyme is found in bacteria and in invertebrate and vertebrate nervous systems. It is the rate-limiting enzyme in determining gamma-aminobutyric acid levels in normal nervous tissues. The brain enzyme also acts on L-cysteate, L-cysteine sulfinate, and L-aspartate. [Gamma-aminobutyric acid]] (GABA) is the major inhibitory neurotransmitter in the central nervous system.

Autoantibodies to GABA is associated with diabetes mellitus type 1.