Hebrew University, Department of Citriculture, Rehovot and Soreq Nuclear Research Center, Yibne, Israel.
Plant Physiol. 1969 May;44(5):631-5. doi: 10.1104/pp.44.5.631.
l-Phenylalanine ammonia-lyase (PAL) activity is low in the external layers (flavedo) of intact mature grapefruit peel. Flavedo discs evince upon incubation increasing PAL activity and ethylene production. Light has no effect in enhancing PAL activity in discs. Exogenous ethylene stimulates PAL activity in the flavedo of intact mature grapefruits (half maximum stimulation at 15 ppm); such activity rapidly decreases when fruit is removed from the ethylene containing atmosphere. Carbon dioxide inhibits both ethylene production and PAL activity of discs; exogenous ethylene only partly relieves PAL inhibition. Cycloheximide inhibits both PAL activity and ethylene production by flavedo discs. The same concentration of cycloheximide also inhibits PAL activity of discs in the presence of exogenous ethylene. Protein synthesis seems therefore to be needed at both levels of ethylene evolution and enhancement of PAL activity.
苯丙氨酸解氨酶（PAL）活性在完整成熟葡萄柚皮的外层（flavedo）中较低。孵育时，flavedo 圆盘表现出 PAL 活性和乙烯生成增加。光照对圆盘 PAL 活性没有增强作用。外源乙烯刺激完整成熟葡萄柚的 flavedo 中 PAL 活性（在 15 ppm 时达到最大刺激的一半）；当果实从含乙烯的大气中取出时，这种活性会迅速下降。二氧化碳抑制圆盘的乙烯生成和 PAL 活性；外源乙烯只能部分缓解 PAL 抑制。环己亚胺抑制 flavedo 圆盘的 PAL 活性和乙烯生成。相同浓度的环己亚胺也抑制存在外源乙烯时圆盘的 PAL 活性。因此，蛋白质合成似乎在乙烯释放和 PAL 活性增强的两个水平上都是必需的。
