The Accumulation of α-Phenylglycine by Mutants of Neurospora Crassa Stimulated by Phenylalanine and Tyrosine

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Abstract
Two mutant strains, UT39 and UT4, obtained from ultra-violet irradiation, were found to be due to single, non-allelic genes. UT39 required phenylalanine or tyrosine, and UT4 tyrosine, for optimal growth. Both strains showed an initial lag period in growth on minimal medium, followed by an increase in growth rate which approached that of the wild type by the eighth day. The addition of tyrosine or phenylalanine to the minimal medium stimulated growth of UT39 after the first two days, and when both tyrosine and phenylalanine were present in equimolar concns. the growth rate of UT39 was approx. the same as that of wild type after 3 days. UT4 was stimulated only by tyrosine. Neither mutant was affected by pH or temperature. A number of substances known to have growth-promoting properties were tested for their effects on the mutants, but none gave as much stimulation as tyrosine or phenylalanine. Leucine, 3-hydroxyanthranilic acid, and tryptophan inhibited growth. Iodoacetate inhibited both mutants and wild type, but the inhibition was partially reversed by tyrosine, phenylalanine or succinic acid. Bacterial assays of culture media in which UT39, UT4 and wild type had grown for 3 days indicated an apparent accumulation of phenylalanine and tyrosine by the mutants, but very little by the wild type. With paper chromatography a spot appeared roughly proportional to the apparent accumulation of the 2 amino acids, but not identical with spots formed by either of them. Cross feeding expts. indicated the production of a growth-stimulating compd. by both mutants. The method of isolating this active factor from UT39 medium is descr. Comparisons between the unknown factor and synthetic dl-alpha-phenylglycine with respect to paper chromatograms and growth experiments indicated that the unknown factor was alpha-phenylglycine. The possible role of alpha-phenylglycine is discussed, as well as its relationship to phenylalanine and tyrosine.

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