Glutamate decarboxylase or glutamic acid decarboxylase (GAD) is an enzyme that catalyzes the decarboxylation of glutamate to GABA and CO2. GAD65 is the isoform with molecular weight of 65 kDa. Karlsen et al. (1991) mapped the GAD2 gene to chromosome 10p13-p11.2 by in situ hybridization. Bu et al. (1992) isolated a cDNA corresponding to the GAD2 gene from a human brain cDNA library. The deduced 585-amino acid protein has a molecular mass of 65 kD. GAD65 is target of autoantibodies in people who later develop type 1 diabetes mellitus or latent autoimmune diabetes.