丝氨酸内肽酶在黄瓜叶片衰老中的作用

采用丝氨酸内肽酶抑制剂和植物生长调节剂处理离体黄瓜叶片，研究了黄瓜叶片暗诱导衰老过程中丝氨酸内肽酶的作用。结果表明，6-BA50μmol／L与丝氨酸内肽酶抑制剂AEBSF能抑制叶片内肽酶活性的升高，延缓蛋白质降解，而ABA50μmol/L则促进了内肽酶活性的升高：其作用效果与AEBSF相反。活性电泳结果显示，黄瓜叶片中检测到6条内肽酶同工酶，其中4条（CEP2、3、4、6）为丝氨酸类型内肽酶，而ABA使丝氨酸内肽酶CEP2、3、4、6的活性明显增强，提示了丝氨酸类型内肽酶在黄瓜叶片衰老过程中具有重要作用。

The Role of Serine Endopeptidase in Cucumber Leaf Senescence

The role of serine endopeptidase in cucumber leaf senescence was studied by using the inhibitor of serine endopeptidase and plant growth regulators (6-BA and ABA) on darkness-induced cucumber leaves. The results showed that the senescence of cucumber leaves were delayed by AEBSF 4-(2-aminoethyl) benzenesulfonyl fluoride hydrochloride], an inhibitor of serine-type endopeptidase, or 6-BA treatment. The chlorophyll contents increased by AEBSF (Fig.3) and the protein degradation of leaves under AEBSF treatment declined more slowly than in the control or under ABA 50 micromol/L treatment (Fig.4), partly because the activities of serine endopeptidases became lower during senescence. However, the activities of endopeptidase in cucumber leaf were increased by ABA 50 micromol/L (Fig.2A), furthermore, the MDA content were also influenced by AEBSF and plant growth regulators (Fig.5). Native gradient PAGE showed that six bands of isoenzymes were detected in cucumber leaves and four bands of which were the type of serine-endopeptidase (Fig.1), and proved that the activities of serine-endopeptidase were inhibited by AEBSF, but enhanced by ABA (Fig.2B) in the leaves. It implies that serine endopeptidases might play an important role in cucumber leaf senescence.