The effect of free amino acid pool levels on the induced synthesis of enzymes.

A previous investigation (Halvorson and Spiegelman, 1952) demonstrated that analogues of amino acids which prevent incorporation from the free amino acid pool into protein also suppress the induced synthesis of maltase in yeast cells. The data obtained led to the conclusion that the quantitatively predominant pathway of induced enzyme formation in nongrowing cells involves the utilization of the internal free amino acids. The importance of amino acids in the formation of enzymes received independent support from work with other enzymatic systems and different biological material. Ushiba and Magasanik (1952) studied the adaptive utilization of myo-inositol by amino acid, purine, and pyrimidine auxotrophs of Aerobacter aerogenes. The response of enzymatic synthesis in resting cells of the mutant types to various kinds of supplementations suggested that the formation of enzymes from amino acids is involved. Pinsky and Stokes (1952) found that the presence of arginine, aspartic acid, and glutamic acid is necessary for the formation of hydrogenlyase in Escherichia coli and conclude that extensive synthesis from free amino acids accompanies enzyme formation. The same conclusion is derived by Monod, Pappenheimer, and CohenBazire (1952) from an ingenious series of experiments with the ,-galactosidase in E. coli to which we shall have reference later. The experiments with yeast cited above established a correlation between the availability of the free amino acid pool and the capacity to synthesize enzyme. Control over protein synthesis from amino acids was achieved by interfering actively with the utilization of components of