inhibition of this enzyme has been the target of many medical studies. The goal of these studies is to find a way to inhibit GABA-T activity, which would reduce the rate that GABA and 2-oxoglutarate are converted to semialdehyde and L-glutamate, thus raising GABA concentration in the brain. There is also a genetic disorder in humans which can lead to a deficiency in GABA-T. This can lead to developmental impairment or mortality in extreme cases. In plants, GABA can be produced as a stress response. Plants also use GABA to for internal signaling and for interactions with other organisms near the plant. In all of these intra-plant pathways, GABA-T will take on the role of degrading GABA. It has also been demonstrated that the succinate produced in the GABA shunt makes up a significant proportion of the succinate needed by the mitochondrion. In fungi, the breakdown of GABA in the GABA shunt is key in ensuring maintaining a high level of activity in the critic acid cycle. There is also experimental evidence that the breakdown of GABA by GABA-T plays a role in managing oxidative stress in fungi. Structural Studies There have been several structures solved for this class of enzymes, given PDB accession codes, and published in peer reviewed journals. At least 4 such structures have been solved using pig enzymes: , , , , and at least 4 such structures have been solved in Escherichia coli: , , , . There are actually some differences between the enzyme structure for these organisms. E. coli enzymes of GABA-T lack an iron-sulfur cluster that is found in the pig model. Active sites Amino acid residues found in the active site of 4-aminobutyrate transaminase include Lys-329, which are found on each of the two subunits of the enzyme. This site will also bind with a pyridoxal 5'􏰌- phosphate co-enzyme. Inhibitors Aminooxyacetic acid Gabaculine Phenelzine Phenylethylidenehydrazine (PEH) Rosmarinic acid Valproic acid Vigabatrin References Further reading External links EC 2.6.1 Pyridoxal phosphate enzymes Enzymes of known structure GABA Glutamate (neurotransmitter)