Induction and stabilization of l-phenylalanine ammonia-lyase activity in Rhodotorula glutinis

Summary

l-Phenylalanine ammonia-lyase (PAL) activity in Rhodotorula glutinis IFO 0559 cells was induced by the addition of 0.5% l-phenylalanine. Activities as high as 15.0×10⁻³ U/mg of cells were obtained. The activity reached a maximum after about 6 h of induction, and then diminished gradually. The enzyme was also induced by d-phenylalanine, l-isoleucine, d-isoleucine, l-leucine, d-leucine, l-valine, l-methionine, l-tryptophan, and l-tyrosine. When 0.1% l-isoleucine was added, high PAL activity was sustained for a relatively long time, but the maximum activity was not increased. Particularly when l-isoleucine and l-valine or l-isoleucine and d-leucine were used as inducers, enzyme activities as high as 22.7 or 24.6×10⁻³ U/mg of cells respectively were obtained. Since the induction of PAL activity by various amino acids was inhibited completely by 50 μM cycloheximide, the induction process was considered to involve de novo synthesis of the enzyme protein.