Kinetics of Chloroplast‐mediated Photoxidation of Diketogulonate*

Habermann, Helen M.; Handel, Mary Ann; McKELLAR, Penelope

doi:10.1111/j.1751-1097.1968.tb08007.x

Cited by 25 publications

(4 citation statements)

References 20 publications

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“…It has been proposed (22) that Mn2+ photooxidation (10,12) by the primary photooxidant of system II is one of a complex series of reactions ultimately leading to formation of an active 02-yielding center. Components capable of rapidly reducing the system II primary photooxidant and/or the presumed higher valency state of Mn generated in photoactivation therefore should inhibit the photoactivation process.…”

Section: Resultsmentioning

confidence: 99%

Effects of Hydroxylamine on Photosystem II

Cheniae¹,

Martin²

1972

Plant Physiol.

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The inactivation of O2evolving centers by NH2OH extraction was shown to be reversible. This reversal required light and manganese. This light-induced restoration of active Oevolving centers was analyzed using three green algae and the blue-green alga, Anacystis nidulans. The following results were obtained:1. In any given illumination, the time course proved first order, the rate being proportional to the number of inactive 02 evolution centers.2. The action spectrum proved to be identical to that of system II. The process was independent of system I and occurred in Scenedesmus mutant No. 8 devoid of this system.3. The quantum efficiency was optimal over a small range of intensities and declined at both lower and higher intensities.The efficiency was half maximal at either 1 or 10 hits per system II trap per second. (5,7,14). This inhibitor causes destruction of 02 centers in algae as well as isolated chloroplasts. With spinach chloroplasts, the loss of 02 evolution capacity is accompanied by a loss of the manganese we associated with the 02 center (5, 7).In isolated chloroplasts the hydroxylamine-induced inactivation of 02 centers appears to be irreversible. With whole algae, however, the effect can be completely reversed by light after removal of NH2OH (5,6). It appeared that the previously noted photoreversal of the effect of NH2OH "extraction" might be similar to the photoactivation of 02 centers in tissue depleted of Mn by growth (4,8).In

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Section: Resultsmentioning

confidence: 99%

Effects of Hydroxylamine on Photosystem II

Cheniae¹,

Martin²

1972

Plant Physiol.

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“…Once formed, the DAs disappears rapidly. In the absence of GSH to recycle it, DAs might be degraded into oxalic acid and L-threonic acids (Habermann et al, 1968). GSSG is also lost.…”

Section: Discussionmentioning

confidence: 99%

Glutathione and ascorbic acid in spinach (Spinacia oleracea) chloroplasts. The effect of hydrogen peroxide and of Paraquat

Law¹,

Charles²,

Halliwell³

1983

Biochemical Journal

819

345

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The stroma of spinach chloroplasts contains ascorbic acid and glutathione at millimolar concentrations. [Reduced glutathione]/[oxidized glutathione] and [ascorbate]/[dehydroascorbate] ratios are high under both light and dark conditions and no evidence for a role of oxidized glutathione or dehydroascorbate in the dark-deactivation of fructose bisphosphatase could be obtained. Addition of H2O2 to chloroplasts in the dark decreases the above ratios, an effect that is reversed on illumination. Addition of Paraquat to illuminated chloroplasts caused a rapid oxidation of reduced glutathione and ascorbate, and apparent loss of dehydroascorbate. Paraquat rapidly inactivated fructose bisphosphatase activity, as assayed under physiological conditions.

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“…In such inhibited or treated chloroplasts water may be replaced by artificial electron donors. Hydroquinones (3 19), phenylenediamines (3 19), benzidine (3 19), semicar bazide (116,319), diphenylcarbazide (293,295), hydrazobenzol (1 16, 117), hydra zine (117,196), hydroxylamine (25,26,116,292), cysteine (163), ascorbate (23,47), diketogulonic acid (104), and Mn++ions (22,24,104,138,169) have been reported as donors. Recently it was shown that H202 (135,136) and tetraphenylboron (129,130) are also electron donors for photosystem II.…”

Section: Artificial Electron Donorsmentioning

confidence: 99%