Glutamate decarboxylase

• OMIM: 605 ​​363
• UniProt: Q99259

Glutamic acid decarboxylase (GAD) hot enzymes in eukaryotes that catalyze the decarboxylation of glutamate to γ -aminobutyric acid ( GABA) and CO2. This is the only way for the biosynthesis of the neurotransmitter GABA. As co- factor pyridoxal phosphate used glutamate decarboxylase. In two human genes are known which encode for enzymes having this activity: GAD1 and GAD2. Mutations in the GAD1 gene can to enzyme deficiency in the brain, and this to spastic cerebral palsy tetraplegischer type 1 ( CPSQ1 ) lead.

In mammals, the glutamate decarboxylase existing in two isoforms GAD67 and GAD65 encoded by the two genes GAD1 and GAD2. Both genes are expressed in cells in the brain, while GAD2 is also expressed in the pancreas. At least two other forms of GAD25 and GAD44 without enzyme activity were detected in the developing brain in embryos.

Catalyzed reaction

CO2

Glutamate is decarboxylated to GABA. Other substrates of the isoform in brain L- Cysteat 3- sulfino -L-alanine and L- aspartic acid.

Antibodies against GAD

Glutamate decarboxylase antibody against the isoform 65 are detectable at the beginning of the disease in 50-70 % of type I diabetics. In particular, in adults with new-onset diabetes, they serve to distinguish an early stage of type 2 type 1 diabetes. (see also LADA = latent autoimmune diabetes in adults. )