The oxygen-evolving complex, (OEC) also known as the water-splitting complex, is a water-oxidizing enzyme involved in the photooxidation of water during the light reactions of photosynthesis. Based on a widely accepted theory from 1970 by Kok, the complex can exist in 5 states: S0 to S4. Photons trapped by photosystem II move the system from state S0 to S4. S4 is unstable and reacts with water to produce free oxygen. Currently, the functional mechanism of the complex is not completely understood. Much of the known data have been collected from flash experiments, EPR, and X-ray spectroscopy.
The OEC appears to have a metalloenzyme core containing both manganese and calcium, with the empirical formula for the inorganic core of Mn4Ca1OxCl1–2(HCO3)y. Other characteristics of it have been reviewed; see
It is suggested that the evolution of the OEC was triggered by the presence of the manganese-containing minerals rancieite and hollandite in the early oceans. The minerals were, it is presumed, assimilated by the early Cyanobacteria, which have incorporated them in the active center of the complex.
Famous quotes containing the word complex:
“It would be naive to think that peace and justice can be achieved easily. No set of rules or study of history will automatically resolve the problems.... However, with faith and perseverance,... complex problems in the past have been resolved in our search for justice and peace. They can be resolved in the future, provided, of course, that we can think of five new ways to measure the height of a tall building by using a barometer.”
—Jimmy Carter (James Earl Carter, Jr.)