Properties and partial purification of kynureninase

Abstract

Production of anthranilic acid is linear with time up to 1 hour. The pH optimum of kynureninase (from Neurospora) was 7.7 and the optimum activity was observed in phosphate buffer, which was shown to be due to the activating effect of phosphate radical. Phosphate did not activate the enzyme in the presence of added pyridoxal phosphate. DL-kynurenine even at a concentration of 4.8 mM in the presence of an optimum amount of pyridoxal phosphate did not inhibit the enzymic activity. Pyridoxal phosphate at a concentration of 0.2 mM did not inhibit the enzyme activity. Mn++ ions activated kynureninase only in the presence of added pyridoxal phosphate, whereas Ca++ ions activated both in the presence and absence of added pyridoxal phosphate. Of the various analogs of vitamin B6 tested, only pyridoxal phosphate and pyridoxamine phosphate activated the enzyme. Pyridoxamine was slightly inhibitory. Evidence has been presented for the presence of functional -SH groups in kynureninase. Kynureninase was purified eightfold.