Photosynthetic oxygen evolution is not reversed at high oxygen pressures: mechanistic consequences for the water-oxidizing complex.

ABSTRACT: We investigated the effects of elevated O(2) pressure on the production of O(2) by photosynthetic organisms in several species of plants, algae, and a cyanobacterium. Using a noninvasive fluorometry technique to monitor sequential turnover of the photosystem II (PSII) reaction center as a function of O(2) pressures, we showed that none of the reactions of water oxidation are affected by elevated O(2) pressures up to 50-fold greater than atmospheric conditions. Thus, the terminal step of O(2) release from the water oxidation complex (S(4) --> S(0) + O(2) + nH(+)) is not reversible in whole cells, leaves, or isolated thylakoid membranes containing PSII, in contrast to reports using detergent-extracted PSII complexes. This implies that there is no thermodynamically accessible intermediate tha

SUBMITTER: Kolling DR 

PROVIDER: S-EPMC2701480 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature