水分胁迫对小麦根细胞质膜氧化还原系统的影响

水分胁迫使小麦根质膜ＮＡＤＨ和ＮＡＤＰＨ的氧化速率及Ｆｅ（ＣＮ）６＾３－和ＥＤＴＡ－Ｆｅ＾３＋的还原速率明显降低。对照与胁迫处理的质膜氧化还原系统活性均不受鱼藤酮、抗霉素Ａ和ＤＣＮ等呼吸链抑制剂的影响。在不加Ｆｅ（ＣＮ）６＾－３作为电子受体时,水杨基羟肟酸（ＳＨＡＭ）可明显刺激质膜ＮＡＤＨ的氧化和Ｏ２吸收速率。水分胁迫促使ＳＨＡＭ刺激的ＮＡＤＨ氧化明显降低,但却使Ｏ２吸收略有上升。     

小麦根质膜原位膜微囊与翻转膜微囊的氧化还原特性比较

用二相法和不连续蔗糖梯度离心分别制得小麦根质膜的原位膜微囊和翻转膜微囊。两者比较可知：质膜内外两侧均表现出较高的氧化还原活性;膜内侧的ＮＡＤ（Ｐ）Ｈ氧化和Ｆｅ（ＣＮ）还原速率高于外侧。质膜内外两侧都能还原ＥＤＴＡ－Ｆｅ３＋,但外侧的还原活性高于内侧。质膜内外两侧均有Ｏ２吸收,同时都可被ＳＨＡＭ刺激,被ＫＣＮ抑制。质膜内侧和外侧都可产生,最适ＰＨ值为６．０;既可被ＳＨＡＭ刺激,也可被ＳＯＤ、过氧化氢酶和ＫＣＮ抑制。     

小麦根质膜原位膜微囊与翻转膜微囊的氧化还原特性比较

用二相法和不连续蔗糖梯度离心分别制得小麦根质膜的原位膜微囊和翻转膜微囊,两者比较可知,质膜内外两侧均表现出较高的氧化还原活性;膜内侧的ＮＡＤ（Ｐ）Ｈ氧化和Ｆｅ（ＣＮ）＾３－６还原速率高于外侧,质膜内外两侧都能还原ＥＤＴＡ－Ｆｅ＾３＋,但外侧的还原活性高于内则,质膜内外两侧均有Ｏ２吸收,同时都可被ＳＨＡＭ刺激,被ＫＣＮ抑制,质膜内侧和外侧都可产生Ｏ＾－２,最适ｐＨ值为６．０既可被ＳＨＡＭ刺激,也可被     

杜氏盐藻细胞质膜氧化还原系统

杜氏盐藻细胞质膜具有氧化ＮＡＤ（Ｐ）Ｈ、还原Ｆｅ（ＣＮ）和Ｏ２的氧化还原系统。当Ｆｅ（ＣＮ）浓度为０．６ｍｍｏｌ／Ｌ时,氧化ＮＡＤＨ的Ｋｍ为９６μｍｏｌ／Ｌ,Ｔｍａｘ为１５９ｎｍｏｌ１０－８ｃｅｌｌｓｍｉｎ－１,最适ｐＨ为８．５。ＴｒｉｔｏｎＸ－１００可促进ＮＡＤＨ和Ｆｅ（ＣＮ）的氧化还原活性。ＮＡＤＨ能促进藻细胞的氧吸收,最适ＰＨ为８．５。在无外源电子供体存在时,细胞质电子供体提供的电子使Ｆｅ（ＣＮ）还原。培养液ＰＨ影响正常呼吸链、交替氧化酶途径和质膜电子传递链的耗氧比例;当有外源ＮＡＤＨ存在时,ＳＨＡＭ明显促进细胞的氧吸收,并且质膜电子传递链的耗氧比例增加。     

杜氏盐藻细胞质膜氧化还原系统与K^＋吸收

杜氏盐藻（Ｄｕｎａｌｉｅｌｌａ ｓａｌｉｎａ）细胞表面存在氧化ＮＡＤＨ 与还原Ｆｅ（ＣＮ）３－６ 的氧化还原系统（ｒｅｄｏｘｓｙｓｔｅｍ ）。该系统在氧化ＮＡＤＨ 时,抑制Ｋ＋ 的吸收,在还原Ｆｅ（ＣＮ）３－６ 时, 促进Ｋ＋ 的吸收,当ＮＡＤＨ 同时存在时, 促进效应最显著, 高达７３５％ 。外源ＮＡＤＨ 促进藻细胞的氧吸收达１６５％ ,而使胞质ｐＨ 下降; 当ＮＡＤＨ 存在时, Ｆｅ（ＣＮ）３－６ 被快速地还原, 同时藻细胞膜外酸化程度增加。质膜Ｈ＋ －ＡＴＰａｓｅ和氧化还原系统的典型抑制剂都不同程度地抑制Ｋ＋ 吸收; 并且钒酸盐对Ｋ＋ 吸收的抑制可以被加入ＮＡＤＨ 和Ｆｅ（ＣＮ）３－６ 而部分恢复, 表明质膜Ｈ＋ －ＡＴＰａｓｅ和氧化还原系统共同参与了细胞Ｋ＋ 的吸收过程     

杜氏盐藻细胞质膜氧化还原系统

杜氏盐藻细胞质膜具的氧化ＮＡＤ（Ｐ）Ｈ,还原Ｆｅ（ＣＮ）＾３－６和Ｏ２的氧化还原系统。当Ｆｅ（ＣＮ）＾３－６浓度为０．６ｍｍｏｌ／Ｌ,氧化ＮＡＤＨ的Ｋｍ为９６μｍｏｌ／Ｌ,Ｖｍａｘ为１５９ｎｍｏｌ１０＾－８ｃｅｌｌｓｍｉｎ＾－１,最适ｐＨ为８．５。ＴｒｉｔｏｎＸ－１００可促进ＮＡＤＨ和Ｆｅ（ＣＮ）＾３－６的氧化还原活性。ＮＡＤＨ能促进藻细胞的氧吸收,最适ｐＨ为８．５。在无外源电子供体存在时,细胞质     

质膜氧化还原系统中的抑制物及其特性

燕麦（Ａｖｅｎａ ｓａｔｉｖａ）质膜氧化还原系统的酶反应进行一段时间后,酶反应速率逐渐降低到零,加入反应底物ＮＡＤＨ、Ｋ３Ｆｅ（ＣＮ）６ 以及质膜（酶）不能使酶反应速率得到恢复,说明酶被抑制． 酶反应的产物可能为ＮＡＤ＋ 、Ｆｅ２＋ 和Ｈ＋ ,加入ＮＡＤ＋ 、Ｋ４Ｆｅ（ＣＮ）６ 和ＨＣｌ不能使酶活力抑制,因此不是产物反馈抑制． 超速离心除去质膜后,发现抑制物存在于反应介质中,这种抑制物的抑制效果随时间延长而降低,所以此抑制物不稳定． 本文首次报道质膜氧化还原系统中存在抑制物     

渗透胁迫下水稻幼苗中叶绿素降解的活性氧损伤作用

水稻（Ｏｒｙｚａ ｓａｔｉｖａ Ｌ．）幼苗在渗透胁迫下,随着胁迫强度的增加及时间的延长,Ｃｈｌ降解加剧,活性氧Ｏ－·２ 、Ｈ２Ｏ２ 及脂质过氧化产物丙二醛（ＭＤＡ）含量明显增加,抗氧化剂抗坏血酸（ＡｓＡ）还原型谷胱甘肽（ＧＳＨ）及胡萝卜素（ＣＡＲ）含量显著降低,叶绿素蛋白复合体（Ｃｈｌ－Ｐｒｏ）结合度松弛． Ｃｈｌ含量的降低和Ｏ－·２ 、Ｈ２Ｏ２ 及ＭＤＡ 含量呈显著的负相关,与ＡｓＡ、ＧＳＨ及ＣＡＲ含量的下降呈良好的正相关性．ＡｓＡ、α－生育酚（ＶｉｔＥ）及甘露醇预处理可使胁迫诱导的ＭＤＡ 增多及Ｃｈｌ降解延缓,而Ｆｅ２＋ 、Ｈ２Ｏ２ 及Ｆｅｎｔｏｎ 反应则刺激ＭＤＡ 增加． Ｆｅｎｔｏｎ 反应可加速Ｃｈｌ降解． 渗透胁迫下水稻幼苗Ｃｈｌ的降解可能主要是由Ｏ－·２ 和Ｈ２Ｏ２ 的代谢产物·ＯＨ氧化损伤之故     

L-SOD发挥活性作用的可能机制

氧化剂、还原剂处理前后,Ｌ－ＳＯＤ的活性及紫外光谱发生变化,Ｈ２Ｏ２使Ｆｅ（Ⅲ）吸收增强,同时钝化Ｌ－ＳＯＤ的活性;加入保险粉后,Ｌ－ＳＯＤ重新活化,Ｆｅ（Ⅲ）吸收减弱．ＮＥＭ封闭Ｃｙｓ后,Ｌ－ＳＯＤ紫外吸收谱发生变化,且活性减弱．说明Ｆｅ辅基及Ｃｙｓ是活性发挥的必需基团．     

细胞质雄性不育水稻的呼吸作用和自由基代谢的关系初探

用呼吸电子传递细胞色素途径的抑制剂氰化钾（ＫＣＮ）与抗氰呼吸途径的抑制剂水杨基氧肟酸（ＳＨＡＭ）处理水稻细胞质雄性不育系（ＣＭＳ）珍汕９７Ａ及其保持系珍汕９７Ｂ的幼穗和花药后,ＫＣＮ使不育系与保持系的超氧阴离子自由基（Ｏ２■）产生受到抑制,不育系的Ｏ２■的形成受抑制较多。ＳＨＡＭ处理则增高Ｏ２■形成,以不育系的增加较多．ＫＣＮ与ＳＨＡＭ处理后都使不育系与保持系的丙二醛（ＭＤＡ）含量升高,ＫＣＮ使保持系的ＭＤＡ含量升高较多,ＳＨＡＭ则使不育系的ＭＤＡ含量升高较多．ＫＣＮ处理后,不育系与保持系的超氧物歧化酶（ＳＯＤ）活性下降,ＳＨＡＭ处理后不育系与保持系的ＳＯＤ活性变化不明显。Ｈ２Ｏ２处理对不育系与保持系幼穗的呼吸速率影响不大．Ｈ２Ｏ２＋ＦｅＳＯ４处理后,使呼吸速率大幅度下降,表明Ｈ２Ｏ２＋ＦｅＳＯ４所形成的羟自由基（ＯＨ）比Ｈ２Ｏ２对呼吸代谢的破坏作用更大。     

Redox activity at the surface of oat root cells

Electron transport activity at the cell surface of intact oat seedlings (Avena sativa L. cv Garry) was examined by measuring the oxidation and/or reduction of agents in the medium bathing the roots. Oxidation of NADH with or without added electron acceptors and reduction of ferricyanide by an endogenous electron donor were detected. The activities appear to be due to electron transfer at, or across, the plasma membrane and not due to reagent uptake or leakage of oxidants or reductants. NADH-ferricyanide oxidoreductase activity was also detected in plasma membrane-enriched preparations from Avena roots. Based on redox responses to pH, various ions, and to a variety of electron donors and acceptors, the results indicate that more than one electron transport system is present at the plasma membrane.     

绿豆线粒体呼吸链在不同电子传递途径中的电子漏

绿豆线粒体的呼喊链在氧化不同义莪时有不同的呼吸速率和电子漏速率,但是Ｏ２＾－／Ｏ２比值较稳定。呼吸链部位Ⅱ的抑制剂抗霉素Ａ对α－酮茂二酸、琥珀酸及苹果本工物时的电子漏速率和Ｏ２＾－／Ｏ２比值都明显的促进作用,说明电子漏发生的位点可能在抗纱Ａ的抑制点之前。呼吸链在氧化外源ＮＡＤＨ时,线料体所产生的地氰化物、鱼藤酮、抗弱Ａ及ＳＨＡＭ都不敏感,而对钙离子的螯合剂ＥＧＴＡ显著敏感。因此,依赖于钙离子的ＮＡ     

Thansplasmalemma redox reactions and ion transport in photosynthetic and heterotrophic plant cells

Extracellular ferricyanide reduction, NADH and ferrocyanide oxidation were investigated by spectrophotometrical method on photosynthetic freshwater plants ( Elodea canadensis Rich., Vallisneria spiralis L., Nitella flexilis L.) and heterotrophic tissues (roots of Triticum vulgare L., Hordeum vulgare L., Zea mays L., Pisum sativum L., Avena sativa L., Allium sativa L., Allium cepa L.). All species had ferricyanide reductase activity. The roots of land plants also carried out extracellular oxidation of NADH and ferrocyanide in contrast to leaves of the freshwater plants. External NADH stimulated ferricyanide reductase activity, but only with those objects that had external NADH oxidase activity. In all species ferricyanide decreased the membrane potential (MP), decreased the membrane resistance measured at a fixed current and inhibited K⁺ influx measured by flame photometry. The factors affecting ferricyanide reductase activity also influenced the inhibitory effect of ferricyanide on the MP and K⁺ transport. These results demonstrate a connection between transport, electrogenic and redox functions of the plasmalemma.     

Evidence for a significant contribution by peroxidase-mediated O2 uptake to root respiration of Brachypodium pinnatum

This study describes the O₂ uptake characteristics of intact roots of Brachypodium pinnatum. In the presence of 25 mM salicylhydroxamic acid (SHAM), concentrations of KCN below 3.5 νM had no effect on the rate of root respiration, whereas in the absence of 25 mM SHAM a significant inhibition of approx. 18% was observed. This indicates that an O₂-consuming reaction, not associated with the cytochrome pathway, the alternative pathway or the “residual component”, operates in the absence of any inhibitors in roots of B. pinnatum. We demonstrate here that this fourth O₂-consuming reaction is mediated by a peroxidase. A peroxidase which catalyzed O₂ reduction in the presence of NADH was readily washed from the roots of B. pinnatum. This peroxidase was stimulated by 5 mM SHAM, whereas ascorbic acid, catalase, catechol, gentisic acid, low concentrations potassium cyanide (3.5 μM), sodium azide, sodium sulfide, superoxide dismutase and high concentrations SHAM (25 mM) inhibited this reaction. Except for high concentrations of SHAM and concentrations of KCN higher than approx. 3.5 μM, these effectors could not be used to inhibit the peroxidase-mediated O₂ uptake in intact roots of B. pinnatum. Concentrations of SHAM below 10 mM stimulated O₂ uptake up to 15% of the control rate, depending on concentration, whereas 25 mM SHAM inhibited O₂ uptake by 35%. The stimulation at low concentrations resulted from a SHAM-stimulated peroxidase activity, whereas 25 mM SHAM completely inhibited both the peroxidase-mediated O₂ uptake and the activity of the alternative pathway. A method is presented for determining the relative contributions of each of the four O₂-consuming reactions, i.e. the cytochrome pathway, the alternative pathway, the “residual component” and the peroxidase-mediated O₂ uptake. The peroxidase-mediated O₂ uptake contributed 21% to the total rate of oxygen uptake in roots of B. pinnatum, the cytochrome pathway contributed 41%, the alternative pathway 14% and the “residual component” 24%.     

Relationship between IAA-induced elongation growth and plasma membrane NADH oxidase in soybean (Glycine max Merr.) hypocotyls

A relationship between the activity of NADH oxidase of the plasma membrane and the IAA-induced elongation growth of hypocotyl segments in etiolated soybean (Glycine max Merr.) seedlings was investigated. The plasma membrane NADH oxidase activity increased in parallel to IAA effect on elongation growth in hypocotyl segments. Actually, NADH oxidase activity was stimulated 3-fold by 1 u,M IAA, and the elongation rate of segments was stimulated 10-fold by 10 iM IAA. The short-term elongation growth kinetics, however, showed that the IAA-induced elongation of hypocotyl segments was completely inhibited by plasma membrane redox inhibitors such as actinomycin D and adriamycin, at 80 μM and 50 μM respectively. In addition, 1 mM actinomycin D inhibited the IAA-stimulated NADH oxidase activity by about 80%. However, adriamycin had no effect on NADH oxidase activity of plasma membrane vesicles. Based on these results, the plasma membrane redox reactions seemed to be involved in IAA-induced elongation growth of hypocotyls, and the redox component responding to IAA was suggested to be NADH oxidase.     

2-Phenyl-beta-lapachone can affect mitochondrial function by redox cycling mediated oxidation

2-Phenyl-beta-lapachone (3,4-dihydro-2-methyl-2-phenyl-2H-naphtho[1,2b]pyran-5,6-dione) (2PBL) is a o-naphthoquinone synthesized as a possible antitumoral agent. The addition of micromolar concentrations of 2PBL to rat liver mitochondria (in the presence of malate-glutamate or succinate, as respiratory substrates): (1) stimulated O(2) consumption in state 4 and inhibited O(2) consumption in state 3, thus decreasing respiratory control index (RCI); and (2) collapsed the mitochondrial membrane potential. The addition of 2PBL to rat liver submitochondrial particles: (1) stimulated NADH oxidation in the presence of rotenone, antimycin, myxothiazol or cyanide; (2) stimulated (.-)O(2)(-) production in the presence of NADH and antimycin; and (3) led to 2PBL semiquinone radical production. Control studies carried out with two p-naphthoquinones, menadione and atovaquone, did not produced equivalent effects. These findings support the hypothesis that 2PBL, undergoes redox cycling and affects mitochondrial function. The 2PBL effect is complex, involving inhibition of electron transfer, uncoupling of oxidative phosphorylation, collapse of mitochondrial membrane potential and (.-)O(2)(-) production by redox cycling. The mitochondrion could be a target organelle for 2PBL cytotoxicity.     

The NADH oxidase activity of the plasma membrane of synaptosomes is a major source of superoxide anion and is inhibited by peroxynitrite

Plasma membrane vesicles from adult rat brain synaptosomes (PMV) have an ascorbate-dependent NADH oxidase activity of 35-40 nmol/min/(mg protein) at saturation by NADH. NADPH is a much less efficient substrate of this oxidase activity, with a Vmax 10-fold lower than that measured for NADH. Ascorbate-dependent NADH oxidase activity accounts for more than 90% of the total NADH oxidase activity of PMV and, in the absence of NADH and in the presence of 1 mm ascorbate, PMV produce ascorbate free radical (AFR) at a rate of 4.0 +/- 0.5 nmol AFR/min/(mg protein). NADH-dependent *O2- production by PMV occurs with a rate of 35 +/- 3 nmol/min/(mg protein), and is a coreaction product of the NADH oxidase activity, because: (i) it is inhibited by more than 90% by addition of ascorbate oxidase, (ii) it is inhibited by 1 micro g/mL wheat germ agglutinin (a potent inhibitor of the plasma membrane AFR reductase activity), and (iii) the KM(NADH) of the plasma membrane NADH oxidase activity and of NADH-dependent *O2- production are identical. Treatment of PMV with repetitive micromolar ONOO- pulses produced almost complete inhibition of the ascorbate-dependent NADH oxidase and *O2- production, and at 50% inhibition addition of coenzyme Q10 almost completely reverts this inhibition. Cytochrome c stimulated 2.5-fold the plasma membrane NADH oxidase, and pretreatment of PMV with repetitive 10 microm ONOO- pulses lowers the K0.5 for cytochrome c stimulation from 6 +/- 1 (control) to 1.5 +/- 0.5 microm. Thus, the ascorbate-dependent plasma membrane NADH oxidase activity can act as a source of neuronal.O2-, which is up-regulated by cytosolic cytochrome c and down-regulated under chronic oxidative stress conditions producing ONOO-.     

Role of plasma membrane redox activities in elongation growth in plants

Comparing isolated plasma membrane vesicles and excised hypocotyl segments from etiolated seedlings of soybean [ Glycine max (L.) Merr. cv. Williams], certain antiproliferative agents that inhibited growth inhibited plasma membrane redox activities. Additionally, auxins that stimulated growth stimulated plasma membrane redox activities. Hormone stimulation was restricted to NADH oxidase (determined from disappearance of NADH) and was given both by isolated plasma membranes and by a soluhilizedenzyme preparation. Comparing IAA, the native auxin regulator, and 2,4-D, a synthetic regulator, stimulation was observed, hut the dose-response curves were different. Yet, the dose-response relationships of both stimulation of auxin growth and stimulation of NADH oxidase were parallel. Inhibition of auxin-induced growth by antiproliferative drugs was more complex. Some, like actinomycin D, preferentially inhibited NADH oxidase (EC 1.6.99.2) but inhibited NADH-ferricya-nide oxido-reductase (EC 1.6.99.3) as well. Others, like adriamycin, inhibited primarily the NADH-ferricyanide oxido-reductase. Therefore, growth control by auxin appeared to involve NADH oxidase as a rate-limiting terminal oxidase to link electron flow from NADH to oxygen. This observation may provide a fundamental difference from animal cells. With the latter, impermeant electron acceptors such as diferric transferrin or ferricyanide fulfill such a role. In plants, these impermeant electron acceptors were without effect on growth or were growth inhibitory.     

Respiration of wheat root cells under simultaneous inhibition of parts I and III of the electron transport chain of mitochondria by rotenone and antimycine A

Respiration of excised roots of 5 day old wheat seedlings with blocked mitochondrial oxidation under simultaneous action of rotenone and antimycine A was studied. A reduced rate of oxygen uptake was observed within the first hour of root treatment inhibitors. However, after a 5 h exposure there was an increase in oxygen uptake, which was prevented by KCN but amplified by malate and ascorbate. The application of inhibitors caused a considerable increase in the respiratory coefficient (RC) up to 2.1, that suggests a significant CO2 release, when the initial sites of mitochondrial electron transport chain were inhibited. RC did not raise, when ascorbate was added in the presence of inhibitors. We assume that inhibition of mitochondrial oxidation at I and III sites of electron transport chain facilitates switching on the alternative paths of reductant translocation to oxygen. Participation of ATPases and redox system of plasma membrane in the response reactions of respiration directed to the restoration of ion, particularly, proton homeostasis in conditions of inhibited mitochondrial oxidation is discussed.