In enzymology, 4-aminobutyrate transaminase (), also called GABA transaminase or 4-aminobutyrate aminotransferase, or GABA-T, is an enzyme that catalyzes the chemical reaction: 4-aminobutanoate + 2-oxoglutarate succinate semialdehyde + L-glutamate Thus, the two substrates of this enzyme are 4-aminobutanoate (GABA) and 2-oxoglutarate. The two products are succinate semialdehyde and L-glutamate. This enzyme belongs to the family of transferases, specifically the transaminases, which transfer nitrogenous groups. The systematic name of this enzyme class is 4-aminobutanoate:2-oxoglutarate aminotransferase. This enzyme participates in 5 metabolic pathways: alanine and aspartate metabolism, glutamate metabolism, beta-alanine metabolism, propanoate metabolism, and butanoate metabolism. It employs one cofactor, pyridoxal phosphate. This enzyme is found in prokaryotes, plants, fungi, and animals (including humans). Pigs have often been used when studying how this protein may work in humans. Enzyme Commission number GABA-T is Enzyme Commission number 2.6.1.19. This means that it is in the transferase class of enzymes, the nitrogenous transferase sub-class and the transaminase sub-subclass. As a nitrogenous transferase, its role is to transfer nitrogenous groups from one molecule to another. As a transaminase, GABA-T's role is to move functional groups from an amino acid and a α-keto acid, and vice versa. In the case of GABA-T, it takes a nitrogen group from GABA and uses it to create L-glutamate. Reaction pathway In animals, fungi, and bacteria, GABA-T helps facilitate a reaction that moves an amine group from GABA to 2-oxoglutarate, and a ketone group from 2-oxoglutarate to GABA. This produces succinate semialdehyde and L-glutamate. In plants, pyruvate and glyoxylate can be used in the place of 2-oxoglutarate. catalyzed by the enzyme 4-aminobutyrate—pyruvate transaminase: (1) 4-aminobutanoate (GABA) + pyruvate succinate semialdehyde + L-alanine (2) 4-aminobutanoate (GABA) + glyoxylate succinate semialdehyde + glycine Cellular and metabolic role The primary role of GABA-T is to break down GABA as part of the GABA-Shunt. In the next step of the shunt, the semialdehyde produced by GABA-T will be oxidized to succinic acid by succinate-semialdehyde dehydrogenase, resulting in succinate. This succinate will then enter mitochondrion and become part of the citric acid cycle. The critic acid cycle can then produce 2-oxoglutarate, which can be used to make glutamate, which can in turn be made into GABA, continuing the cycle. GABA is a very important neurotransmitter in animal brains, and a low concentration of GABA in mammalian brains has been linked to several neurological disorders, including Alzheimer's disease and Parkinson's disease. Because GABA-T degrades GABA, the