PHOTOPRODUCTION OF AMMONIA AND HYDROGEN-PEROXIDE

Conversion of solar energy into suitable redox energy by photosynthetic systems capable of using water as the electron donor is at the present time of great interest and significance. There are, in principle, two different kinds of redox pairs whose reduction may be coupled with the photooxidation of water to molecular oxygen : those which have potential levels similar to the hydrogen electrode and must accept electrons at the reducing side of photosystem I, and those which have positive potentials and can interact at the reducing side of photosystem II. The second group includes the couples ammonia-nitrate and hydrogen peroxide-oxygen, which exhibit standard redox potentials equal or higher than +0.3 V. Both can steadily operate in vivo and in vitro under aerobic conditions and do not have an ATP requirement. © 1979.