Abstract:

The characterization of senescence-associated endopeptidase (EP) isoenzymes in wheat (Triticum aestivum L. var. Yangmai 158) leaves during dark-induced senescence was performed. It was found that there was much higher endoproteolytic activity in dark-induced wheat leaves than in control. Six endopeptidase isoenzymes (EP1-EP6) were identified by natural gradient杙olyacrylamide gel electrophoresis (PAGE) co-polymerized gelatin in the gel, five of which (EP1, EP2, EP4, EP5 and EP6) were only detected in senescing leaves. Treatment with 6-benzylaminopurine (6-BA) delayed the expression of these EP isoenzymes and abscisic acid (ABA) accelerated it. The activity of EP3 could be detected at a wider range of pH and temperature levels while EP4, EP5 and EP 6 could be only detected at pH 4-5 and 30 45 ℃, EP1 and EP2 at pH 3 5 and 30 ℃ 45 ℃. All of the EP isoenzymes showed high thermal stability, especially EP3, EP5 and EP6 which still had activities even by incubation at 55 ℃ for 1 h. By using different class-specific inhibitors, EP1 and EP2 were characterized as metal-dependent cysteine-proteases, EP4 as a serine-protease.

小麦叶片暗诱导衰老期间内肽酶的特性
芮 琪 徐朗莱
(南京农业大学生命科学学院, 南京210095)
 

摘要: 研究了小麦 (Triticum aestivum L. cv. Yangmai 158)叶片暗诱导衰老期间内肽酶同工酶的变化及其部
分生化特性,发现叶片衰老期间,内肽酶活性升高,同时出现5种新的内肽酶同工酶（EP1、EP2、EP4、EP5、EP6）。6-苄氨基嘌呤(6-BA)处理能延缓这些同工酶的出现,而脱落酸（ABA）处理则加速它们的表达。衰老期间小麦叶片内的6种内肽酶同工酶（EP1-EP6）中的EP1、EP2、EP4、EP5、EP6呈现活性的pH及温度范围较窄,而EP3有活性的pH范围和温度范围均较宽,且EP3在嫩叶、老叶中均有活性。另外,EP3、EP5、EP6对热不太敏感。蛋白酶抑制剂实验表明，EP1、EP2 是需金属离子的半胱氨酸型内肽酶,EP4是丝氨酸型内肽酶。
关键词: 内肽酶；叶衰老；小麦