Purification and properties of 4-aminobutyrate 2-ketoglutarate aminotransferase from pig liver.

4-Aminobutyrate-transaminase (4-aminobutyrate: 2-oxoglutarate amino-transferase, EC 2.6.1.19) from pig liver has been purified to electrophoretic homogeneity. It has a molecular weight of about 110 000 and is composed of two subunits of the same molecular weight but of different charges. Two forms of pig liver 4-aminobutyrate-transaminase were isolated by DEAE-cellulose chromatography and designated as 4-aminobutyrate-transaminase I and 4-aminobutyrate-transaminase II, corresponding to a cationic and anionic form. Some physical and kinetic properties of liver enzyme were compared to those of brain enzyme and no significant difference were found, except for their sedimentation coefficients and the charges of their subunits. The role of 4-aminobutyrate-transaminase in liver remains a matter of speculation, but could be related to a metabolic function.