The kinetics and mechanism of oxidation of reduced spinach ferredoxin by molecular oxygen and its reduced products

Hosein, Barbara; Palmer, Graham

doi:10.1016/0005-2728(83)90045-2

Cited by 36 publications

(18 citation statements)

References 31 publications

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“…Electron transport and ATP synthesis rates decline in parallel (Table I) The differences seen in the presence and absence of NADP+ may be explained by the differing redox conditions imposed upon cyclic flow by noncyclic electron transport. In the absence of NADP, ferredoxin is forced to reduce only 02, and because this reaction is quite slow (9), it must result in larger pools of reduced ferredoxin and PQ. The addition of low concentrations of DCMU will cause a partial oxidation of both pools.…”

Section: Methodsmentioning

confidence: 99%

Regulation of Cyclic Photophosphorylation during Ferredoxin-Mediated Electron Transport

Hosler¹,

Yocum²

1987

Plant Physiol.

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Addition of ferredoxin to isolated thylakoid membranes reconstitutes electron transport from water to NADP and to 02 (the Mehler reaction).This electron flow is coupled to ATP-synthesis, and both cyclic and noncyclic electron transport drive photophosphorylation. Under conditions where the NADPH/NADP+ ratio is varied, the amount of ATP synthesis due to cyclic activity is also varied, as is the amount of cyclic activity which is sensitive to antimycin A. Partial inhibition of photosystem II activity with DCMU (which affects reduction of electron carriers of the interphotosystem chain) also affects the level of cyclic activity. The results of these experiments indicate that two modes of cyclic electron transfer activity, which differ in their antimycin A sensitivity, can operate in the thylakoid membrane. Regulation of these activities can occur at the level of ferredoxin and is governed by the NADPH/NADP ratio.Evidence has accumulated for the existence of PSI cyclic photophosphorylation activity and its importance for CO2 fixation in chloroplasts (6,7,15,24,25). One of the remaining questions about PSI cyclic electron flow pertains to the mechanism by which the chloroplast regulates cyclic and noncyclic electron transport in order to maintain the necessary balance between ATP and NADPH for CO2 fixation activity. Partial inhibition of PSII electron flow has been shown to stimulate cyclic photophosphorylation in intact chloroplasts ( 11,12,15) and in isolated thylakoids supplied with ferredoxin (3) as long as anaerobic conditions are maintained. This 'poising' effect presumably reflects a redistribution of electron flow in favor of reduced ferredoxin to PQ3 (with possible intermediate carriers) concurrent with restriction of electron flow from PSII to PQ. Addition of NADPH to isolated thylakoids in the presence of ferredoxin also stimulates cyclic photophosphorylation (1), and the NADPH/NADP+ ratio has been proposed to regulate the partitioning of electrons between the cyclic and noncyclic pathways at the level of ferredoxin (1,2,16,17,21 cyclic photophosphorylation, catalyzed by electron transport from water to ferredoxin/02 or to ferredoxin/NADP+. These experiments, performed under aerobic conditions using saturating light, provide a closer approximation of the activity of PSI cyclic photophosphorylation in vivo than does measurement of a cyclic reaction poised independently of noncyclic electron transport. Our previous studies on this reconstituted electron transport system have shown that electron transport to either ferredoxin/02 or to ferredoxin/NADP+ produces elevated P/O ratios (1.6 versus 1.25 with MeV as the acceptor); the increased P/O ratio is due to the induction, by ferredoxin, of a cyclic or Q-loop electron transfer mechanism (10). This work also suggests the existence of two separate pathways of cyclic photophosphorylation: one pathway is characterized by sensitivity to antimycin A and the requirement for a substantial pool of reduced ferredoxin, while a second pathway is insensitive to anti...

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Section: Methodsmentioning

confidence: 99%

Regulation of Cyclic Photophosphorylation during Ferredoxin-Mediated Electron Transport

Hosler¹,

Yocum²

1987

Plant Physiol.

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“…Takagi et al (2016) demonstrated that the ROS production site rather than the quantity of ROS is crucial for PSI photoinhibition. Reduced ferredoxin does not play a role in O 2 $ 2 generation at PSI, since the reaction of reduced ferredoxin with oxygen is rather slow (Hosein and Palmer, 1983).…”

Section: Advancesmentioning

confidence: 99%

Redox- and Reactive Oxygen Species-Dependent Signaling into and out of the Photosynthesizing Chloroplast

Türkan²,

2016

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Photosynthesis is a high-rate redox metabolic process that is subjected to rapid changes in input parameters, particularly light. Rapid transients of photon capture, electron fluxes, and redox potentials during photosynthesis cause reactive oxygen species (ROS) to be released, including singlet oxygen, superoxide anion radicals, and hydrogen peroxide. Thus, the photosynthesizing chloroplast functions as a conditional source of important redox and ROS information, which is exploited to tune processes both inside the chloroplast and, following retrograde release or processing, in the cytosol and nucleus. Analyses of mutants and comparative transcriptome profiling have led to the identification of these processes and associated players and have allowed the specificity and generality of response patterns to be defined. The release of ROS and oxidation products, envelope permeabilization (for larger molecules), and metabolic interference with mitochondria and peroxisomes produce an intricate ROS and redox signature, which controls acclimation processes. This photosynthesis-related ROS and redox information feeds into various pathways (e.g. the mitogen-activated protein kinase and OXI1 signaling pathways) and controls processes such as gene expression and translation.

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“…In chloroplasts, the Fe atoms of Fd seem to fulfill the role of metal catalysts (Elstner and Konze, 1974;. The hydroxyl radical can also be formed from hydrogen peroxide and reduced Fd (Hosein and Palmer, 1983;Bowyer and Camilleri, 1985). The hydroxyl radical can initiate self-propagating peroxidative reactions leading to the destruction of membrane lipids and of DNA, and hence to extensive tissue damage (see Bowler et al, 1992, for review).…”

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confidence: 99%

Factors Affecting the Enhancement of Oxidative Stress Tolerance in Transgenic Tobacco Overexpressing Manganese Superoxide Dismutase in the Chloroplasts

Slooten¹,

Capiau²,

et al. 1995

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Two varieties of tobacco (Nicofiana fabacum var PBD6 and var SR1) were used to generate transgenic lines overexpressing Mnsuperoxide dismutase (MnSOD) in the chloroplasts. The overexpressed MnSOD suppresses the activity of those SODs (endogenous MnSOD and chloroplastic and cytosolic Cu/ZnSOD) that are prominent in young leaves but disappear largely or completely during aging of the leaves. The transgenic and control plants were grown at different light intensities and were then assayed for oxygen radical stress tolerance i n leaf disc assays and for abundance of antioxidant enzymes and substrates in leaves. Transgenic plants had an enhanced resistance to methylviologen (MV), compared with control plants, only after growth at high light intensities. I n both varieties the activities of FeSOD, ascorbate peroxidase, dehydroascorbate reductase, and monodehydroascorbate reductase and the concentrations of glutathione and ascorbate (all expressed on a chlorophyll basis) increased with increasing light intensity during growth. Most of these components were correlated with M V tolerance. It is argued that SOD overexpression leads to enhancement of the tolerance to MV-dependent oxidative stress only if one or more of these components is also present at high levels. Furthermore, the results suggest that i n var SR1 the overexpressed MnSOD enhances primarily the stromal antioxidant system.The photosynthetic electron transport chain in higher plant chloroplasts contains, at the acceptor side of PSI, a number of auto-oxidizable enzymes. For example, Fd in the reduced state can react with oxygen, yielding the superoxide anion radical (OJ (Furbank and Badger, 1982;Asada and Takahashi, 1987), and it has been shown that superoxide is also generated in the aprotic membrane interior (Elstner and Frommeyer, 1978;Takahashi and Asada, 1988). Superoxide does not seem to be particularly toxic, although it does inactivate a number of metal-containing enzymes such as Fd-linked nitrate reductase, catalase, and peroxidases

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The kinetics and mechanism of oxidation of reduced spinach ferredoxin by molecular oxygen and its reduced products

Cited by 36 publications

References 31 publications

Regulation of Cyclic Photophosphorylation during Ferredoxin-Mediated Electron Transport

Regulation of Cyclic Photophosphorylation during Ferredoxin-Mediated Electron Transport

Redox- and Reactive Oxygen Species-Dependent Signaling into and out of the Photosynthesizing Chloroplast

Factors Affecting the Enhancement of Oxidative Stress Tolerance in Transgenic Tobacco Overexpressing Manganese Superoxide Dismutase in the Chloroplasts

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