[Effect of aromatic amino acids on levorin biosynthesis].

Aromatic amino acids, such as tryptophan and phenylalanine inhibit biosynthesis of levorin, while tyrosine stimulates it. The studies with resting cells showed that the changes in the level of the antibiotic production in the presence of the above amino acids were connected with their effect on the process of levorin biosynthesis and not on the growth of the antibiotic-producing organism. The changes in the content of the bound p-aminoacetophenone in the mycelium of Str. levoris correlated with the level of the antibiotic production. The amount of free p-aminoacetophenone in the mycelium of Str. levoris increased in the presence of the aromatic amino acids. It is suggested that the increase in the synthesis of levorin in the medium with addition of tyrosine was connected with inhibition of prefenic acid synthetase. Tryptophan must have an inhibitory effect on antranylate synthetase. Its effect on levorin synthetase is also possible.