Studies on the polarography of proteins. 1. The relation of wave heights to protein concentration and the origin of wave III

tryptophan peroxidase, superimposed upon the slower removal of kynurenine by kynureninase lacking an adequate concentration of its coenzyme.SUMMARY 1.Under optimal conditions, the average kynu- reninase activity ofnormal rat liver was 11 1 Iumoles L-kynurenine removed/g.dry wt./hr.The activity in pyridoxine-deficient rats was decreased by lack of the coenzyme to 5 9,moles/g.dry wt./hr.The kynureninase was not increased adaptively in the animals by administration of kynurenine or tryptophan.2. For comparison, kynurenine can be formed by the tryptophan peroxidase in normal rat liver at an average rate of 9 3 ,tmoles/g.dry wt./hr., and this rate can be adaptively increased tenfold by trypto- phan administration to the animal.3. The abnormal accumulation of tryptophan metabolites can therefore be attributed to a relative inadequacy of kynurenine removal, due to a de- crease of kynureninase through lack of its coenzyme, or to an adaptive increase of the kynurenine-forming enzyme, tryptophan peroxidase, or to both.These mechanisms can account for the marked accumulation of metabolites in even normal animals given supplemental tryptophan, as well as in pyridoxine-deficient animals.