Required for the degradation of gamma-aminobutyric acid (GABA), which is important for utilization of GABA as nitrogen source and for oxidative stress tolerance. Deaminates GABA to succinate semialdehyde, which in turn is converted to succinate by the succinate-semialdehyde dehydrogenase UGA2 (By similarity). May be involved in an alternative, arginase-independent arginine degradation pathway via GABA (Probable). 2-oxoglutarate + 4-aminobutanoate = L-glutamate + succinate semialdehyde Amino-acid degradation; L-arginine degradation. Homodimer and homotetramer. Induced 4.7-fold in an arginase-negative strain during exponential growth. Belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family.