Endopeptidase Isoenzyme Characteristics in Cucumis sativus Leaves During Dark-induced Senescence

Endopeptidase Isoenzyme Characteristics in Cucumis sativus Leaves During Dark-induced

Senescence

Peng Zhang; Fei Wang; Lie-Feng Zhang; Qi Rui; Lang-Lai Xu

【期刊名称】《《植物学报（英文版）》》 【年(卷),期】2007(049)004

【摘要】The changes and characteristics of endopeptidase (EP) isoenzymes in cucumber (Cucumis sativus L.) leaves during dark-induced senescence were investigated by activity staining after gradient-polyacrylamide gel electrophoresis (G-PAGE) containing co-polymerized gelatin as substrate. The results showed that both the chlorophyll and the protein contents of leaves were decreased, and the protein degradation was correlated with the increase of proteolytic activity during the course of leaf senescence. Meanwhile, nine cucumber endopeptidases isoenzymes (CEP) with 140, 120, 106, 94, 76, 55, 46, 39 and 35 kDa molecular weights were detected. Four of these, CEP2, 3, 4 and CEP9 appeared all the time, but the changes of the activity were different during incubation. Another four CEPs (CEP5, 6, 7 and CEP8) whose activities increased with dark-induced time were only detected in senescent leaves.Furthermore, the biochemical properties of these nine CEP were also characterized. All the CEPs had high activities from 35 ℃ to 45 ℃, and the optimum temperature was found to be 40 ℃. However,