Abstract
Peak production of phenylalanine and tyrosine ammonia lyase activity occurs during late logarithmic phase in the growth of batch cultures of the yeast, Sporobolomyces roseus. There is some evidence that two enzymes are involved although the production and activity of each enzyme appears to be under common control. Replacement media containing either phenylalanine or tyrosine stimulate production of both enzymes whereas cinnamic acid represses their formation. The activities of both enzymes are also inhibited by cinnamic or p-coumaric acids.