Generates GABA from glutamate. Likely to be responsible for the metabolism of glutamate via the GABA shunt to succinate during growth. H(+) + L-glutamate = 4-aminobutanoate + CO2 Homohexamer. Expressed in growing cells, its mRNA continuously decreases during development. Highly expressed during phagocytosis of non-pathogenic bacteria. Belongs to the group II decarboxylase family.