Pak Caroline, van Doorn Wouter G
Agrotechnology and Food Innovations (A & F), Wageningen University and Research Centre, PO Box 17, 6700 AA Wageningen, the Netherlands.
New Phytol. 2005 Feb;165(2):473-80. doi: 10.1111/j.1469-8137.2004.01226.x.
Visible senescence of the flag tepals in Iris x hollandica (cv. Blue Magic) was preceded by a large increase in endoprotease activity. Just before visible senescence about half of total endoprotease activity was apparently due to cysteine proteases, somewhat less than half to serine proteases, with a minor role of metalloproteases. Treatment of isolated tepals with the purported serine protease inhibitors AEBSF [4-(2-aminoethyl)-benzenesulfonyl fluoride] or DFP (diisopropyl-fluorophosphate) prevented the increase in endoprotease activity and considerably delayed or prevented the normal senescence symptoms. The specific cysteine protease-specific E-64d reduced maximum endoprotease activity by 30%, but had no effect on the time to visible senescence. Zinc chloride and aprotinin reduced maximum endoprotease activity by c. 50 and 40%, respectively, and slightly delayed visible senescence. A proteasome inhibitor (Z-leu-leu-Nva-H) slightly delayed tepal senescence, which indicates that protein degradation in the proteasome may play a role in induction of the visible senescence symptoms. It is concluded that visible senescence is preceded by large-scale protein degradation, which is apparently mainly due to cysteine- and serine protease activity, and that two (unspecific) inhibitors of serine proteases considerably delay the senescence symptoms.
在荷兰鸢尾（品种：蓝魔）中，旗瓣明显衰老之前，内切蛋白酶活性大幅增加。就在明显衰老之前，总内切蛋白酶活性的大约一半显然归因于半胱氨酸蛋白酶，略少于一半归因于丝氨酸蛋白酶，金属蛋白酶起次要作用。用所谓的丝氨酸蛋白酶抑制剂AEBSF [4-(2-氨基乙基)-苯磺酰氟] 或DFP（二异丙基氟磷酸酯）处理离体的花瓣，可阻止内切蛋白酶活性的增加，并显著延迟或阻止正常衰老症状的出现。特异性半胱氨酸蛋白酶特异性抑制剂E-64d使最大内切蛋白酶活性降低了30%，但对出现明显衰老的时间没有影响。氯化锌和抑肽酶分别使最大内切蛋白酶活性降低了约50%和40%，并略微延迟了明显衰老。蛋白酶体抑制剂（Z-亮-亮-缬氨酸）略微延迟了花瓣衰老，这表明蛋白酶体中的蛋白质降解可能在明显衰老症状的诱导中起作用。得出的结论是，明显衰老之前会发生大规模蛋白质降解，这显然主要归因于半胱氨酸和丝氨酸蛋白酶活性，并且两种（非特异性）丝氨酸蛋白酶抑制剂可显著延迟衰老症状。
