Changes in the enzymatic composition of liver. II. Influence of hormones on picolinic carboxylase and tryptophan peroxidase.

In Paper I (1) it was reported that the amount of the liver enzyme, picolinic carboxylase, is greatly increased in diabetic rats, while other related enzymes are not changed greatly. In this paper some of the factors that influence the level of this enzyme in rat liver are described. A major role was found for adrenal steroids, which are required for the increase to occur. The increase in enzyme level is not a simple response to cortisone-like hormones, however, as the extent of the response is determined by other physiological factors. In general the changes of picolinic carboxylase parallel those reported for glucose-6-phosphatase (2). The finding of the same type of change in enzyme level with enzymes that have unrelated functions and occur in different cell fractions indicates that the effects of certain hormones may be to alter greatly the enzymatic composition of cells and not merely to influence the activities of individual enzymes.