Relationships and Interactions between Phenylalanine Ammonia-lyase, Phenylalanine Ammonia-lyase Inactivating System, and Anthocyanin in Apples1

Abstract

Abstract Low temperature (6°C) in light stimulated the accumulation of phenylalanine ammonia-lyase (PAL) and anthocyanin and reduced the level of phenylalanine ammonia-lyase inactivating system (PALS-IS) in the skin of whole apples. Without light, anthocyanin synthesis did not take place in the skin of whole apples, and the level of PAL was found to be very low. In skin disks held in the dark, however, PAL activity increased but no anthocyanin was synthesized. In both the light and dark conditions, PAL-IS in the skin of whole apples was about 3.5 times higher than that in the apple skin disks after 44 hours of incubation at 18°. In the skin of whole apples, cycloheximide (10, 25, and 50 μm), chloramphenicol (50, 100, and 200 μm), and puromycin (10 and 25 μm) increased the accumulation of PAL and anthocyanin and reduced the level of PAL-IS. In the apple skin disks, cycloheximide (0.1, 1.0, 5.0, and 10.0 μm) and chloramphenicol (10.0 and 50.0 μm) inhibited the accumulation of PAL and anthocyanin to varying degrees. Puromycin had little effect on the accumulation of PAL but strongly inhibited the synthesis of anthocyanin. None of the antibiotics, at the concentrations tested, had any effect on the accumulation of PAL-IS in apple skin disks.