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Author Nakano, Y., Asada, K. file  url
Title Hydrogen Peroxide is Scavenged by Ascorbate-specific Peroxidase in Spinach Chloroplasts Type Journal Article
Year 1981 Publication Plant and Cell Physiology Abbreviated Journal  
Volume 22 Issue 5 Pages 867-880  
Keywords Spinach; Chloroplasts; Hydrogen peroxide; Peroxidase; Ascorbate  
Abstract Intact spinach chloroplasts scavenge hydrogen peroxide with a peroxidase that uses a photoreductant as the electron donor, but the activity of ruptured chloroplasts is very low [Nakano and Asada (1980) Plant & Cell Physiol. 21 : 1295]. Ruptured spinach chloroplasts recovered their ability to photoreduce hydrogen peroxide with the concomitant evolution of oxygen after the addition of glutathione and dehydroascorbate (DHA). In ruptured chloroplasts, DHA was photoreduced to ascorbate and oxygen was evolved in the process in the presence of glutathione. DHA reductase (EC and a peroxidase whose electron donor is specific to L-ascorbate are localized in chloroplast stroma. These observations confirm that the electron donor for the scavenging of hydrogen peroxide in chloroplasts is L-ascorbate and that the L-ascorbate is regenerated from DHA by the system: photosystem I-->ferredoxin-->NADP-->glutathione. A preliminary characterization of the chloroplast peroxidase is given.  
Call Number Serial 2173  
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Author Tischer, W.; Strotmann, H. file  url
Title Relationship between inhibitor binding by chloroplasts and inhibition of photosynthetic electron transport Type Journal Article
Year 1977 Publication Biochimica et Biophysica Acta Abbreviated Journal Biochim Biophys Acta  
Volume 460 Issue 1 Pages 113-125  
Keywords Atrazine/metabolism/*pharmacology; Binding Sites; *Carbamates; Chloroplasts/drug effects/*metabolism; Diuron/pharmacology; Electron Transport; Herbicides/metabolism/*pharmacology; Kinetics; Mathematics; Photophosphorylation/*drug effects; Plants; Triazines/metabolism/*pharmacology  
Abstract The binding of radioactively labelled atrazin, metribuzin and phenmedipham by broken chloroplasts was studied. From the double-reciprocal plots (bound vs. free inhibitors) a high affinity binding reaction is graphically isolated which is related to the inhibition of photosynthetic electron transport. It is concluded that the specific binding sites correspond to the electron carrier molecules which are attacked by the inhibitors. The relative concentration of specific binding sites is 1 per 300-500 chlorophyll molecules. The binding of the labelled substances is competitively inhibited by each of the indicated unlabelled substances, by DCMU and by several pyridazinone derivatives. These results suggest that triazines, triazinones, pyridazinones, biscarbamates and phenylureas interfere with the same electron carrier of the photosynthetic electron transport chain, according to the same molecular mechanism.  
Call Number Serial 544  
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