Purification and Properties of GABA Transaminase from Bovine Brain

A 4500-fold purification of 4-aminobutyrate (GABA) transaminase from bovine brain tissue has been achieved for the first time by a combination of ammonium sulfate fractionation, CM-Sephadex, DEAE-Sephadex and hydroxyapatite chromatographic methods. The final chromatography step yields a homogeneous preparation of high specific activity (18 units/mg). The molecular mass of the native enzyme was estimated to be approximately 100,000 on gel filtration. The subunit molecular mass was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis to be 50,000. These results indicate that GABA transaminase purified from bovine brain is a dimeric protein made up of identical subunits. The circular dichroism (CD) analysis showed that the enzyme contains 43% α-helical structure.