ABAT (4-aminobutyrate aminotransferase) is a mitochondrial enzyme that catalyzes the conversion of gamma-aminobutyrate (GABA) to succinate semialdehyde, a critical step in GABA catabolism 1. The enzyme also converts L-beta-aminoisobutyrate to methylmalonate semialdehyde and functions as part of the mitochondrial 4-aminobutyrate:2-oxoglutarate transaminase complex, requiring pyridoxal phosphate as a cofactor 1. ABAT plays a crucial role in maintaining balanced mitochondrial nucleotide pools necessary for mitochondrial DNA synthesis and maintenance 2. Pathogenic variants in ABAT cause GABA-transaminase deficiency, leading to GABA accumulation and neurological dysfunction 1. This deficiency is associated with developmental and epileptic encephalopathy, complex partial epilepsy, developmental disability, cardiomyopathy, and blindness 1. The enzyme's role in GABA metabolism is fundamental to maintaining the balance between neuronal excitation and inhibition in the brain; mutations disrupt this balance and result in seizures and cognitive impairment 1. ABAT deficiency represents one of several genetic abnormalities affecting GABA metabolism that contribute to epilepsy pathogenesis, making it clinically significant for accurate diagnosis and treatment of metabolic forms of epilepsy.