Amino-acid sequence of rat liver kynureninase.

Amino-acid sequence of kynureninase purified from rat liver cytosol was determined by an amino-acid sequencer. The enzyme was degraded to small peptides with cyanogen bromide, TPCK-trypsin, endoproteinase Glu-C, lysyl endoprotease and alpha-chymotrypsin. The enzyme subunit consisted of 464 amino acids, and the molecular weight of subunit was determined to be 52,510. The coenzyme pyridoxal phosphate-binding residue was lysine of which position was 276, and the N-terminal residue was N-acetylmethionine. The homology search between this enzyme and the other pyridoxal phosphate-dependent enzymes showed that kynureninase was similar to mitochondrial aspartate aminotransferase, and also to cystathionine gamma-synthase and gamma-lyase to a lesser extent.