Net utilization of free amino acids during the induced synthesis of maltozymase in yeast.

Previous investigations with yeast have examined the effect of variations in the availability of the internal free amino acids on the capacity of resting cells to synthesize maltase. Control over the free amino acid pool as a source of nitrogen for protein synthesis was achieved by the use of analogues of amino acids (Halvorson and Spiegelnan, 1952) and by nitrogen starvation and replenishment procedures (Halvorson and Spiegelman, 1953). It was found that interference with the utilizability of the free amino acids or the absence of an adequate supply resulted in inhibition of enzyme synthesis. These data as well as those obtained with bacteria (Pinsky and Stokes, 1952; Monod et al., 1952; Ushiba and Magasanik, 1952) lead to the conclusion that the primary pathway of induced enzyme formation involves synthesis of new enzyme from free amino acids. Halvorson and Spiegelman (1952) were able to exhibit a striking correlation between enzyme forming capacity and the level of the internal free amino acid pool. From the viewpoint of these results it seemed possible that the free amino acid pool of cells actively synthesizing a new enzyme might well be demonstrably different from the pool in cells held under identical conditions but not subject to the induction of a new enzyme. It was of interest therefore to study the reverse of the problem thus far considered and examine the effect of enzyme synthesis on the free amino acid pool. A simple comparison of the free amino acid pools under these two conditions, however, is complicated by the observations of Roine (1947) which were confirmed amply in the investigations