Elicitation of phenylalanine ammonia lyase in Daucus carota L. by oligogalacturonides released from sodium polipectate by homogeneous polygalacturonase

α-d-Galacturonide oligomers were prepared by partial hydrolysis of sodium polypectate with homogeneous polygalacturonase from Aspergillus niger. The oligomers were able to induce a strong increase in the activity of phenylalanine ammonia-lyase in Daucus carota cell suspension cultures, probably as a result of increased de novo synthesis of the enzyme. The induction of phenylalanine ammonia-lyase (PAL) was transient and occurred rapidly after treatment with oligo-galacturonides. The concentration of oligogalacturonides capable of inducing enzyme activity was 6 × 10−6 M and lower. Oligomers with degrees of polymerization from 2 to 5 were purified to homogeneity and assayed for PAL-inducing activity. The pentamer possessed the highest activity and the trimer the lowest. Mono- and digalacturonate did not exhibit any activity.