Photosynthetic Production of Hydrogen Peroxide by Anacystis nidulans

A sensitive assay based upon fluorescence of scopoletin allowed continuous recording of H(2)O(2) 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 H(2)O(2) production. Size of the H(2)O(2) burst was decreased by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea, by low O(2), and by certain Calvin cycle intermediates; it was increased by high light intensity, CO(2) depletion, Calvin cycle inhibitors (as iodoacetamide), cold shock, carbonyl cyanide m-chlorophenylhydrazone, and certain organic acids as glycolate). The H(2)O(2) 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 CO(2) reduction and, instead, reacts with oxygen. H(2)O(2) 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.