A simplified procedure for the purification of rat liver tyrosine aminotransferase.
Rat liver tyrosine aminotransferase was purified by chromatography on CM-Sephadex C-50 and DEAE-cellulose, (NH4)2SO4 fractionation and gel filtration on Sephadex G-200. Livers from 400 rats can be easily worked up by this procedure. Furthermore, this purification method has the advantage that hepatic tryptophan 2,3-dioxygenase, which, like tyrosine aminotransferase, is induced by glucocorticosteroids, can be purified from the same homogenate. Tyrosine aminotransferase purified by this method was shown to be specific for 2-oxoglutarate. Its subunits have a molecular weight of 45 000. The following "apparent" Michaelis constants were determined: L-tyrosine, 1.7 X 10(-3) M; 2-oxoglutarate, 5.9 X 10(-4) M; and pyridoxal 5'-phosphate, 2.1 X 10(-6) M. Tyrosine aminotransferase, depleted of its cofactors, binds 4 molecules of pyridoxal 5'-phosphate per 90 000 daltons with a KA of 2.2 X 10(5) M-1.
D000818:Animals; D005260:Female; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D008970:Molecular Weight; D011485:Protein Binding; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D051381:Rats; D014444:Tyrosine Transaminase / Q000302:isolation & purification*
D011732:Pyridoxal Phosphate; D014444:Tyrosine Transaminase