Induction of Phenylalanine Ammonia-lyase in Xanthium Leaf Disks. Photosynthetic Requirement and Effect of Daylength

Abstract

A cycloheximide-sensitive increase in the activity of phenylalanine ammonia-lyase (EC 4.3.1.5) occurs in Xanthium leaf disks exposed to light. Radioactive ammonia-lyase has been isolated by means of sucrose density gradient centrifugation and starch gel electrophoresis from disks fed l-isoleucine-U-¹⁴C or l-arginine-U-¹⁴C. The incorporation of radioactive amino acids into phenylalanine ammonia-lyase together with the inhibitory effects of cycloheximide indicate that the observed increase in enzyme activity involves the induction of lyase synthesis.