ALTERED REGULATION OF AROMATIC AMINO-ACID BIOSYNTHESIS IN BETA-PHENYLETHYL-ALCOHOL-OVERPRODUCING MUTANTS OF SAKE YEAST SACCHAROMYCES-CEREVISIAE

Mutants resistant to the phenylalamine analogues omicron-fluoro-DL-phenylalanine (OFP) or p-fluoro-DL-phenylalanine (PFP) were isolated from a sake yeast, Saccharomyces cerevisiae Kyokai No. 9. They produced large amounts of beta-phenylethyl alcohol and its acetate ester, which are rose-like flavor components. The tyrosine-dependent isozyme of 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHP synthase; EC 4.1.2.15), in one of the OFP-resistant mutants was released from feedback inhibition by tyrosine. This mutant overproduced tyrosine in addition to beta-phenylethyl alcohol and phenylalanine in minimal medium. In the PFP-resistant mutants, the activity of prephenate dehydrogenase (EC 1.3.1.12) was decreased to 5% of that in the wild type strain, while its DAHP synthase was increased four-fold. The tyrosine-dependent isozyme of this mutant was still sensitive to tyrosine. This mutant also overproduced tryptophan and phenylalanine in addition to beta-phenylethyl alcohol in minimal medium.