The Activities of Some Enzymes of Tryptophan Metabolism in Fetal, Neonatal and Adult Rat Liver and Kidney. I. Kynureninase and Kynurenine Aminotransferase.

Kynureninase activity in fetal tissue of rat is two thirds the level of the adult, while kynurenine aminotransferase (L-kynurenine: 2-oxoglutarate aminotransferase, EC. 2. 6. 1. 7) activity could not be observed at all in fetal tissue. The latter began to arise after birth and reached the adult level at 50 g of body weight. This fact suggests that anthranilic acid in fetal tissue might have some special significnace. It is also suspectable that some hormones regulate these enzymes which catalyze tryptophan metabolism. The administration of estradiol-17 fJ inhibited the activities of these two enzymes in vivo, especially kynurenine aminotransferase. Progesterone did not show such an effect.