Purification of the native form of tyrosine aminotransferase from rat liver

A procedure that provides a homogeneous, native form of tyrosine aminotransferase (l-tyrosine: 2-oxoglutarate aminotransferase, EC 2.6.1.5) from rat liver in exceptionally high yield is described. This goal is accomplished by rapidly inactivating the lysosomal converting factor that generates two additional, lower-molecular-weight forms of tyrosine aminotransferase, and by separating the native enzyme from the altered forms by chromatography on carboxymethyl-Sephadex C-50 and an optional hydroxylapatite step. Homogeneity appears to be achieved after the carboxymethyl-Sephadex C-50 step, and the final yield of the enzyme exceeds 30%.