Département de Biologie, Faculté des Sciences de Tunis El Manar, Unité de Recherche de Biologie et Physiologie Cellulaires Végétales, 1060 Tunis, Tunisia.
Planta. 2011 Oct;234(4):857-63. doi: 10.1007/s00425-011-1468-y. Epub 2011 Jul 9.
The effects of cadmium (Cd) on aminopeptidase (AP) activities and Leucine-AP (LAP) expression were investigated in the roots of tomato (Solanum lycopersicum L., var Ibiza) plants. Three-week-old plants were grown for 10 days in the presence of 0.3-300 μM Cd and compared to control plants grown in the absence of Cd. AP activities were measured using six different p-nitroanilide (p-NA) substrates. Leu, Met, Arg, Pro and Lys hydrolyzing activities increased in roots of Cd-treated plants, while Phe-pNA cleavage was not enhanced after Cd treatments. The use of peptidase inhibitors showed that most of the Leu-pNA hydrolyzing activity was related to one or several metallo-APs. Changes in Lap transcripts, protein and activities were measured in the roots of 0 and 30-μM Cd-treated plants. LapA transcript levels increased in Cd-treated roots, whereas LapN RNAs levels were not modified. To assess amount of Leu-pNA hydrolyzing activity associated with the hexameric LAPs, LAP activity was measured following immunoprecipitation with a LAP polyclonal antiserum. LAP activity increased in Cd-treated roots. There was a corresponding increase in LAP-A protein levels detected in 2D-immunoblots. The role of LAP-A in the proteolytic response to Cd stress is discussed.
研究了镉（Cd）对番茄（Solanum lycopersicum L.，var Ibiza）植物根中氨肽酶（AP）活性和亮氨酸-AP（LAP）表达的影响。将 3 周龄的植物在存在 0.3-300 μM Cd 的情况下生长 10 天，并与在不存在 Cd 的情况下生长的对照植物进行比较。使用六种不同的对硝基苯胺（p-NA）底物测量 AP 活性。Cd 处理植物的根中 Leu、Met、Arg、Pro 和 Lys 水解活性增加，而 Phe-pNA 切割在 Cd 处理后没有增强。使用肽酶抑制剂表明，大多数 Leu-pNA 水解活性与一种或几种金属 AP 有关。在 0 和 30-μM Cd 处理的植物的根中测量了 Lap 转录物、蛋白质和活性的变化。Cd 处理根中的 LapA 转录物水平增加，而 LapN RNA 水平没有改变。为了评估与六聚体 LAPs 相关的 Leu-pNA 水解活性量，用 LAP 多克隆抗血清进行免疫沉淀后测量 LAP 活性。Cd 处理的根中 LAP 活性增加。在 2D-免疫印迹中检测到相应的 LAP-A 蛋白水平增加。讨论了 LAP-A 在应对 Cd 胁迫的蛋白水解反应中的作用。
