蚕豆种子超氧物歧化酶的纯化及性质

蚕豆种子粗提液经乙醇－氯仿混合物处理、丙酮沉淀、ＤＥＡＥ－纤维素层析和Ｓｅｐｈａｒｏｓｅ６Ｂ层析,获得比活性为２８５２单位ｍｇ－１蛋白的超氧物歧化酶．经聚丙烯酰胺凝胶电泳证明酶已纯化到均一程度．该酶对ＫＣＮ和Ｈ２Ｏ２敏感,说明它为Ｃｕ,Ｚｎ－ＳＯＤ．酶分子量和亚基分子量分别为３１０００和１４４００,说明它是由两个相同亚基组成。该酶在７０℃以下和在ｐＨ５—９条件下稳定．紫外区最大吸收峰为２７３．５ｎｍ。     

水稻叶片的衰老与超氧物歧化酶活性及脂质过氧化作用的关系

研究了从抽穗开花到籽粒成熟过程中,水稻植株顶部三片叶子的超氧物歧化酶(SOD),脂质过氧化产物丙二醛(MDA)含量及二磷酸核酮糖羧化酶活性的变化。实验结果表明:叶片的衰老伴随着 SOD 活性、RuBP 羧化酶活性及叶绿素含量的降低、丙二醛含量显著增高。分离了三个 SOD 的同工酶,证明为 Cu—Zn SOD。观察了 SOD 同工酶在叶片老化及酶液存放不同时间中的变化。讨论了叶片衰老过程中氧自由基对酶及质膜的损伤影响。     

超氧物歧化酶（SOD）在植物逆境和衰老生理中的作用

在大气污染、低温、干旱、盐分、强光辐射等逆境胁迫及衰老进程中,植物体内活性氧的产生能力大于清除能力。相对过量的活性氧影响生物膜和其它生物大分子的结构或功能。SOD等活性氧清除剂具有维持活性氧代谢平衡、保护膜结构的功能。     

杂交稻及其三系叶片衰老过程中SOD、CAT活性和MDA含量的变化

对杂交水稻及其三系主茎第11叶叶片自然衰老过程中超氧物歧化酶(SOD)、过氧化氢酶(CAT)和丙二醛(MDA)含量的变化进行了研究,结果表明:叶片衰老过程中,SOD和CAT活性下降,MDA的含量增加,可作为衰老特征的叶绿素和可溶性蛋白质含量明显下降;SOD的活性和MDA的含量变化相对应;CAT活性大幅度下降与SOD之间的不平衡,致使O_2~-代谢中间产物累积而引起膜的损伤。不育系的衰老进程比杂交水稻、恢复系和保持系慢,其SOD和CAT活性明显高于其它三者,可能是不育系不易早衰的原因之一。     

凤眼莲超氧物歧化酶活性与抗寒性的关系

低温使凤眼莲叶内SOD活性降低,同时叶组织电解质外渗增加和TTG的还原力降低。用适量的联吡啶季胺盐(Paraquat)处理凤眼莲叶片,使超氧物歧化酶活性增强,则能减轻低温引起的伤害。试验提供了超氧物歧化酶与抗寒性有关的直接证据.     

萌发绿豆子叶衰老期间蛋白质代谢的变化

萌发绿豆子叶自然衰老过程中可溶性蛋白质含量一直下降;从衰老开始到衰老前期,总游离氨基酸含量明显上升;但游离氨基酸各组分在子叶衰老期间的变化趋势并不相同。~3H-亮氨酸掺入蛋白质试验和多聚核糖体的相对量及其与总核糖体的比值(P/T)测定都证明在子叶衰老前期有蛋白质的新合成。子叶衰老期间。氨肽酶活性明显降低;而以酪蛋白为底物的蛋白水解酶活性却急剧上升,承担着催化蛋白质降解的主要功能。     

绿豆子叶衰老期间核酸代谢的变化

萌发绿豆的子叶自然衰老期间,核酸含量降低,RNA降低的幅度比DNA大。电泳分析结果表明,子叶衰老期间细胞核主带DNA明显降低;而迁移慢的卫星带DNA变化不大。在RNA各组分中,18S rRNA从衰老前期就开始降低;25S rRNA和4～5S小分子RNA到衰老后期才缓慢下降。DNase和RNase活性在子叶整个衰老期间都明显升高,是导致核酸含量下降的主要原因。~3H-核苷掺入试验表明,核酸的合成速率在子叶衰老前期有所上升,到衰老后期又降低。poly(A)~ -mRNA含量在子叶开始衰老时明显上升。     

小麦叶片暗诱导衰老期间内肽酶的特性

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。     

小麦叶片暗诱导衰老期间内肽酶的特性

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.     

表油菜素内酯对绿豆幼叶衰老的促进作用

表油菜素内酯（ｅｐｉＢＲ）０．０５ｍｇ／Ｌ能促进绿豆幼叶的衰老,其叶绿素和蛋白质含量均明显低于对照。绿豆幼叶经ｅｐｉＢＲ处理后,可使过氧化物酶活性明显增加,但同工酶谱无变化;超氧化物歧化酶（ＳＯＤ）和过氧化氢酶（ＣＡＴ）活性随ｅｐｉＢＲ处理时间的延长而降低。ｅｐｉＢＲ能促进丙二醛（ＭＤＡ）含量增加,而其含量与ＳＯＤ和ＣＡＴ活性是显著负相关。     

蚕豆萎蔫病毒2号分离物侵染对蚕豆叶片光合活性和叶绿体超微结构的影响

研究了受蚕豆萎蔫病毒2号（Broad bean wilt virus 2,BBWV2）中国分离物B935和欧洲分离物PV131侵染的蚕豆（Vicica faba）叶片光合特性、叶绿素荧光诱导动力学参数和叶绿体超微结构变化。感病蚕豆叶绿素含量减少,叶绿素a／b比逐步降低;光合气体交换参数Pn值和Gs值降低,Ci值升高;叶绿素荧光诱导动力学参数Fv/Fm、FV＇/Fm＇、ΦPSII、qP值均有不同程度降低,NPQ值升高;光合器结构遭到不同程度的破坏,B935侵染后叶绿体发育不良,片层结构疏松,PVl31侵染后叶绿体肿胀变圆,片层结构疏松瓦解。与B935相比,PV131侵染对以上各参数的变化有更大影响,且对叶绿体的破坏更为严重。实验结果表明BBWV2不同分离物对光系统II（PSII）的抑制作用与光合器受损程度相关。     

不同品种(系)小豆根系活力与叶片衰老的关联研究

以高产小豆品种(系)‘2000-75’、‘冀红9218’和低产品种(系)‘红宝1号’、‘湾选1号’为材料,测定小豆开花至成熟期,根系与始花节位叶片生长指标、保护酶活性、可溶性蛋白含量等变化,分析其根系与始花叶协同衰老的相关性,以揭示小豆根系活力与地上部叶片衰老之间的关系。结果表明:(1)各品种(系)开花后,植株根系伤流强度随着花后生育进程的推进呈单峰增长趋势,但根系活力的衰老起始期晚于叶片功能的衰退开始期。(2)从开花至成熟期,小豆根系活力与叶片中超氧化物歧化酶、过氧化氢酶、叶绿素含量、可溶性蛋白、叶片净光合速率都存在正相关关系,与丙二醛含量呈负相关关系。(3)与低产品种相比,高产小豆品种(系)‘2000-75’和‘冀红9218’的根系活力强,叶片功能期持续时间长,叶绿素含量下降速度慢,保护性酶含量高,使花后小豆的功能叶捕获光能的能力增强,从而形成较高光合能力的小豆群体,最终获得高产。     

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

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, the activities of CEPs were not detected below 25 ℃ or over 60 ℃. The activity bands appeared at a wide range of pH from 5.0 to 9.0, but the optimum pH was found at 7.0. No CEPs were detected at pH 4 or pH 10. By inhibition analysis we concluded that CEP2, 3, 4 and CEP9 were serine endopeptidases and CEP6 was a kind of cysteine protease. It is suggested that serine endopeptidases might play a major role in cucumber leaf senescence, and for the first time, six senescencerelated endopeptidases （CEP1, 5, 6, 7, 8 and 9） were found in cucumber leaves.     

蚕豆叶片尿囊素酶性质初探

酰尿输出型蚕豆有一定程度合成和同化酰脲的能力(刘承宪和黄维南1987a),蚕豆叶片尿囊素酶(B-ALNase)和酰脲输出型大豆叶片尿囊素酶(S-ALNase)(Thomas等1983)不同,是热敏感的(刘承宪和黄维南 1987b)。我们进一步分离和纯化B-ALNase,并作了初步的鉴