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Pseudocyclic photophosphorylation

Besides these external processes, formation of ROS may also take place intrac-ellularly. Photooxidative stress, including UVB, stimulates various cellular processes leading to the production of superoxide radicals and hydrogen peroxide, as well as singlet-oxygen and hydroxyl radicals. The sources and production sites of ROS are mainly related to photosynthetic activities such as the pseudocyclic photophosphorylation and the Mehler reaction, which stimulate the accumulation of hydrogen peroxide (Asada 1994 Elstner 1990). [Pg.277]

Fig 1 shows the effect of pig adenodoxin in cyclic and pseudo cyclic photosynthetic phosphorylations. Although these reactions are specific of photosynthetic aganisms, the animal ferredoxin can replace plant ferredoxin vnth a rather good efficiency in the case of pseudocyclic photophosphorylation. On the otha hand, adkenodoxin is unable to donate electrons in the cydic pathway. These observations suggest that this animal ferredoxin can be photaeduced through PSI and the assodated bound iron sulfa centas. [Pg.2931]

Foyer and Halliwell (1976) proposed that GSH serves indirectly as an important source of reducing equivalents for mopping up firee radicals produced photochemically by leakage of electrons from photosystem I via fenedoxin into O2 (i.e., pseudocyclic photophosphorylation ). The superoxide radical produced by this activity is highly reactive, especially toward lipids, which are major constituents of chloroplasts. The sequence of reactions involved in the detoxification process is shown in Fig. 10. It involves dismutation of superoxide to H2O2 catalyzed by superoxide dismutase followed by reduction of HjOj to... [Pg.368]

AUen JF Cyclic, pseudocyclic and noncyclic photophosphorylation new links in the chain. Trends Plant Sci 8(1) 15—19, 2003. [Pg.252]

Applying the criteria of Gimmler (1977) for the characterization of the three types of photophosphorylation it is rather difficult to determine the type of the phosphorylation observed. The cyclic phosphorylation can be excluded on account of the fully reduced state of the algae as a consequence of the long anaerobiosis, the applied high light intensity and its insensitivity towards complete inhibition of an electron transport from PS II by DCMU. DCMU prevents photosynthetic O2 evolution and the non-cyclic electron transport. As the observed ATP increase is not affected by DCMU both non-cyclic and pseudocyclic phosphorylation should be ruled out. [Pg.783]


See other pages where Pseudocyclic photophosphorylation is mentioned: [Pg.1546]    [Pg.1546]    [Pg.345]    [Pg.1546]    [Pg.1546]    [Pg.345]   


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Pseudocycles

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