Photosynthetic Production of Hydrogen Peroxide by Anacystis nidulans1

AUTOR(ES)

Patterson, C. O. Pat

RESUMO

A sensitive assay based upon fluorescence of scopoletin allowed continuous recording of H2O2 production in illuminated intact cells of Anacytis nidulans. Onset of illumination was followed by a 5 to 10 second lag, a burst of very rapid production continuing for up to 5 minutes, and finally a slow and continuing steady rate of H2O2 production. Size of the H2O2 burst was decreased by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea, by low O2, and by certain Calvin cycle intermediates; it was increased by high light intensity, CO2 depletion, Calvin cycle inhibitors (as iodoacetamide), cold shock, carbonyl cyanide m-chlorophenylhydrazone, and certain organic acids as glycolate). The H2O2 burst was explained by the following hypothesis: a low potential reductant is produced more rapidly than it can be used in the normal pathway to CO2 reduction and, instead, reacts with oxygen. H2O2 production is regarded as a metabolic defect observable in Anacystis most dramatically during the transition from a very low rate of oxidative dark metabolism to a high rate of photosynthetic metabolism.

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