EFFECT OF FLUOROPHENYLALANINE ON L‐PHENYLALANINE AMMONIA‐LYASE ACTIVITY IN AVENA COLEOPTILES

Publisher Website
Google Scholar
Abstract
Treatment of etiolated A vena coleoptile apices with several concentrations of DL‐p‐fluorophenylalanine, previously reported to stimulate coleoptile elongation, caused marked reductions in chlorogenic acid content. Levels of this analogue which had no growth effect caused no detectable alteration of chlorogenic acid accumulation. Evidence is presented which indicates that chlorogenic acid levels may reflect extractable L‐phenylalanine ammonia‐lyase activity in this tissue. Incubation of coleoptiles with 5 mm DL‐p‐fluorophenylalanine resulted in significantly lowered extractable ammonia‐lyase activity compared to controls. Similar treatment of tissues with the ortho isomer also caused a reduction of enzyme activity but to a lesser extent. Treatment with the meta isomer had no effect on extractable enzyme activity. These findings provide further evidence for the hypothesis that DL‐p‐fluorophenylalanine stimulates coleoptile elongation by lowering L‐phenylalanine ammonia‐lyase activity and the subsequent biosynthesis of potentially inhibitory low molecular weight phenols.