Acetazolamide inhibition of photosystem II in isolated spinach chloroplasts

Swader, J. A.; Jacobson, Bernard

doi:10.1016/s0031-9422(00)89968-9

Cited by 48 publications

(22 citation statements)

References 8 publications

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“…Previous studies of CO, and HCO; use have relied on inhibition of external CA using CA inhibitors (Moroney et al, 1985;Williams and Turpin, 1987;Gehl et al, 1990). Although these experiments have enabled conclusions to be drawn regarding the presence of HCO, transport, it is difficult to interpret the effects of CA inhibitors on whole- cell Phs since these compounds may inhibit interna1 CA activity (Williams and Turpin, 1987), PSII activity (Swader and Jacobsen, 1972), or transport activity (Price and Badger, 1989). The use of acid-grown C. saccharophila enables the examination of Phs and the role of external CA without the use of inhibitors.…”

Section: Discussionmentioning

confidence: 99%

Quantification of the Contribution of CO2, HCO3-, and External Carbonic Anhydrase to Photosynthesis at Low Dissolved Inorganic Carbon in Chlorella saccharophila

Williams

Colman

1995

Plant Physiol.

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Section: Discussionmentioning

confidence: 99%

Quantification of the Contribution of CO2, HCO3-, and External Carbonic Anhydrase to Photosynthesis at Low Dissolved Inorganic Carbon in Chlorella saccharophila

Williams

Colman

1995

Plant Physiol.

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“…Chlorophyll was determined by the method of Arnon (1). Ferredoxin was isolated by the method of San Pietro (15) as modified by Swader and Jacobson (18). The 02 evolving capacity of the chloroplasts was destroyed by a mild heat treatment as described by Hinkson and Vernon (6).…”

Section: Methodsmentioning

confidence: 99%

The Cupric Ion as an Inhibitor of Photosynthetic Electron Transport in Isolated Chloroplasts

1972

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The role of copper in photosynthetic organisms depends greatly on its concentration. Copper, as cupric ion, in trace amounts is an essential micronutrient for algae and higher plants (17,20) and is an essential constituent of several enzymes such as polyphenol oxidase (3) and plastocyanin (8), a component of photosynthetic electron transport. Concentrations higher than 1 /tm are increasingly toxic to algal and higher plant tissues (4, 13). Cupric sulfate has been extensively used as an algaecide since the beginning of the century (12). The cupric ion has been shown to be an inhibitor of photosynthesis in algal cells (4,11,16) and to inhibit photosynthetic electron transport in isolated chloroplasts (5, 10).The mechanism by which the Cu'+ inhibits the photosynthetic apparatus has been only partially elucidated thus far. The data on inhibition of photosynthesis in isolated chloroplasts gives an incomplete picture of the specific sites of inhibition in the electron transport chain. Macdowall (10) He studied the effect of light intensity on inhibition and concluded that the light reactions were directly affected by Cu21. In addition, Haberman (5) using chloroplasts from Phytolacca americanca showed that both the Hill and Mehler reactions were inhibited by Cu2+ but that the Mehler reaction was inhibited by lower concentrations of the ion.In contrast to Macdowall, Haberman concluded that Cu2+ was inhibiting a dark reaction and did not alter the reactions associated with the photoacts. She observed that Mn2+ added at a concentration of 0.5 mm reduced the inhibition of chloroplasts by Cu2+ and postulated that the Cu2+ was affecting the site of manganese function in 02 evolution. Recently exogenous Mn2+ has been shown to donate electrons after the water oxidation site of photosystem II of isolated chloroplasts (2), suggesting that, at high concentrations, manganese functions in a way other than its primary role in the water oxidation act.This work was conducted with the purpose of resolving the sites of Cu2+ inhibition in photosynthetic electron transport. Since previous work and our preliminary experiments pointed to the fact that photosystem II is preferentially inhibited by Cu2+ emphasis was given to finding the specific sites of inhibition within this photosystem. MATERIALS AND METHODSChloroplasts were prepared from market-grown spinach (Spinacia olercacea L.) as described by Robinson and Stocking (14). MnCl2 was excluded from the grinding and resuspending media in the preparations where Mn2+ was used as an electron donor. Chlorophyll was determined by the method of Arnon (1). Ferredoxin was isolated by the method of San Pietro (15) as modified by Swader and Jacobson (18). The 02 evolving capacity of the chloroplasts was destroyed by a mild heat treatment as described by Hinkson and Vernon (6). The chloroplasts were uncoupled by adding ammonium ions following the principle discovered by Krogman et al. (9).The normal reaction media for studying 02 evolution had the following composition in a total volume of 2...

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“…Although most CA inhibitors are quite specific, it has been shown in chloroplasts that some CA inhibitors, in addition to inhibiting CA activity, can cause a small decrease in the rate of PSII electron transport (22). Both PSI and PSII appear to be required for Ci uptake in cyanobacteria (11,18 (Fig.…”

Section: Effect Of Ez On Psii Electron Transportmentioning

confidence: 99%

Ethoxyzolamide Inhibition of CO₂-Dependent Photosynthesis in the Cyanobacterium Synechococcus PCC7942

Price

Badger²

1989

Plant Physiol.

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Cells of the cyanobacterium, Synechococcus PCC7942, grown under high inorganic carbon (C,) conditions (1% C02; pH 8) were found to be photosynthetically dependent on exogenous CO2.This was judged by the fact that they had a similar photosynthetic affinity for CO2 (Ko.5[CO2] of 3.4-5.4 micromolar) over the pH range 7 to 9 and that the low photosynthetic affinity for C, measured in dense cell suspensions was improved by the addition of exogenous carbonic anhydrase (CA). The CA inhibitor, ethoxyzolamide (EZ), was shown to reduce photosynthetic affinity for CO2 in high Ci cells. The addition of 200 micromolar EZ to high Ci cells increased Ko.5(CO2) from 4.6 micromolar to more than 155 micromolar at pH 8.0, whereas low C, cells (grown at 30 microliters CO2 per liter of air) were less sensitive to EZ. EZ inhibition in high and low C, cells was largely relieved by increasing exogenous C, up to 100 millimolar. Lipid soluble CA inhibitors such as EZ and chlorazolamide were shown to be the most effective inhibitors of CO2 usage, whereas water soluble CA inhibitors such as methazolamide and acetazolamide had little or no effect. EZ was found to cause a small drop in photosystem 11 activity, but this level of inhibition was not sufficient to explain the large effect that EZ had on CO2 usage. High C cells of Anabaena variabilis M3 and Synechocystis PCC6803 were also found to be sensitive to 200 micromolar EZ. We discuss the possibility that the inhibitory effect of EZ on CO2 usage in high Cl cells of Synechococcus PCC7942 may be due to inhibition of a 'CA-like' function associated with the CO2 utilizing C, pump or due to inhibition of an intemal CA activity, thus affecting CO2 supply to ribulose bisphosphate carboxylase-oxygenase.It is now well documented that cyanobacteria possess an inducible CO2 concentrating mechanism (CCM2) which functions to elevate internal CO2 levels around Rubisco (5,6,10,13,17 levels of Ci (7,15). Although most research has centered upon characterizing the high affinity HCO-uptake system, it has been known for some time that CO2 is often a more efficient substrate for the CCM than HCO3 (6,7,24) Nevertheless, the most recent model for the CCM postulates a pivotal role for a HCO3 transporter on the plasma membrane (24). In this proposal the ability to utilize CO2 is accommodated for by the addition of a 'CA-like' moiety that converts CO2 to HCO3 in close proximity to the HCO3 pump. It was assumed that CO2 acts as a better substrate due to a higher diffusion rate into the periplasmic space than the charged HCO-ion. The best evidence for this model is that in low CO2 grown cells ofAnabaena variabilis M3, a low concentration (1O .M) of the CA inhibitor, EZ, inhibits CO2 uptake more than HCOT uptake (24). Unfortunately this type of evidence is not generally applicable to other cyanobacteria, such as Synechococcus sp., which are virtually unaffected by 10 to 100 ,uM EZ (9).Recent studies have verified that low CO2 grown cyanobacteria possess the ability to transport or utilize both CO2 and HCO3 (...

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Acetazolamide inhibition of photosystem II in isolated spinach chloroplasts

Cited by 48 publications

References 8 publications

Quantification of the Contribution of CO2, HCO3-, and External Carbonic Anhydrase to Photosynthesis at Low Dissolved Inorganic Carbon in Chlorella saccharophila

Quantification of the Contribution of CO2, HCO3-, and External Carbonic Anhydrase to Photosynthesis at Low Dissolved Inorganic Carbon in Chlorella saccharophila

The Cupric Ion as an Inhibitor of Photosynthetic Electron Transport in Isolated Chloroplasts

Ethoxyzolamide Inhibition of CO₂-Dependent Photosynthesis in the Cyanobacterium Synechococcus PCC7942

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Acetazolamide inhibition of photosystem II in isolated spinach chloroplasts

Cited by 48 publications

References 8 publications

Quantification of the Contribution of CO2, HCO3-, and External Carbonic Anhydrase to Photosynthesis at Low Dissolved Inorganic Carbon in Chlorella saccharophila

Quantification of the Contribution of CO2, HCO3-, and External Carbonic Anhydrase to Photosynthesis at Low Dissolved Inorganic Carbon in Chlorella saccharophila

The Cupric Ion as an Inhibitor of Photosynthetic Electron Transport in Isolated Chloroplasts

Ethoxyzolamide Inhibition of CO2-Dependent Photosynthesis in the Cyanobacterium Synechococcus PCC7942

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Ethoxyzolamide Inhibition of CO₂-Dependent Photosynthesis in the Cyanobacterium Synechococcus PCC7942