Wound-induced Phenylalanine Ammonia-Lyase in Potato Tuber Tissue

Development of Enzyme Activity and Effects of Antibiotics

Abstract

Phenylalanine ammonia-lyase [EC 4.3.1.5] activity increased rapidly after a 3-hr lag period in potato tuber (Solanum tuberosum L. cv. May Queen) disks incubated in a suitable medium in the dark at 25°. The activity reached a maximum after incubation for about 40 hr. The effects of actinomycin D, 6-methylpurine, cycloheximide, chloramphenicol, and mitomycin C on the induction of phenylalanine ammonia-lyase were investigated during incubation of the disks. Actinomycin D, 6-methylpurine, and cycloheximide all inhibited the formation of phenylalanine ammonia-lyase, though cycloheximide was the most effective at low concentrations. Application of actinomycin D for the initial lag period (3 hr) caused strong inhibition; however, if it was supplied later it did not inhibit but actually increased phenylalanine ammonialyase formation. In contrast, cycloheximide was effective over most of the incubation period. Chloramphenicol and mitomycin C did not inhibit phenylalanine ammonialyase induction, but markedly stimulated it. Light was not an essential factor for phenylalanine ammonia-lyase induction in the wounded tissue.