Studies on activity of tryptophan aminotransferase in rat liver.

Abstract

1) A Lineweaver-Burk plot of tryptophan aminotransferase activity in the supernatant fraction from rat liver gave a hyperbolic curve. This suggested that the activity might be due to the simultaneous actions of two or more enzymes with different Km values.2) On DEAE-cellulose column chromatography of the supernatant from normal rat liver, tryptophan aminotransferase activity separated into two peaks, while that from the liver of rats after tryptophan or cortisol injection separated into three peaks. The second peak eluted from the latter seems to be an inducible enzyme. No aspartate, alanine, tyrosine, kynurenine, histidine or phenylalanine aminotransferase activities were detected in this fraction. The first peak eluted from DEAE-cellulose column had aspartate aminotransferase activity and the third peak had tyrosine aminotransferase activity.3) On DEAE-cellulose column chromatography, the tryptophan aminotransferase activity in the supernatant fractions from the kidneys and hearts of normal rats, tumor cells (AH-130) and the livers of tumor-bearing rats showed the same elution pattern as that from the liver of rats after tryptophan or cortisol injection. The Km values for tryptophan of these enzymes in the second peaks were all similar. These results suggest that the aminotransferase enzyme in the second peaks from all these sources may be the same kind of tryptophan specific enzyme.