Transaminase that degrades gamma-amino butyric acid (GABA). 4-aminobutanoate + pyruvate = L-alanine + succinate semialdehyde 4-aminobutanoate + glyoxylate = glycine + succinate semialdehyde Not detected in roots, stems, flowers or leaves of healthy plants. Up-regulated by blast fungus, UV, mechanical wounding, salicylic acid and abscisic acid, but not by methyl jasmonate. Belongs to the class-III pyridoxal-phosphate-dependent aminotransferase family.