What is the importance of manganese in calvin cycle?
Answers
Although the process of light energy conversion to chemical form by specialized plant cell organelles, the chloroplasts, is well understood, many contemporary investigations have been concerned with the catalytic role played by manganese in oxygen evolution. Current views of the photosynthetic electron transport chain or the so-called “Z-scheme” intermediates identify the cytochromes b6, b-559 and f, the chlorophyll linked primary electron acceptor and donors of photosystems -I and -II and a number of e.p.r. distinct iron-sulfur centres involved in non cyclic and possibly cyclic electron transfer pathways. The accumulation of four redox equivalents leads to the oxidation of water to yield molecular oxygen by a water splitting metalloenzyme (designated -Y) which involves at least two manganese atoms per molecule of enzyme. During the four electron oxidation of water, e.p.r. and proton relaxation evidence suggest the two manganese atoms undergo redox changes between manganese(II) and manganese(III) states. A number of proposed manganese model systems exhibiting the features required by the well known S-state mechanism of oxygen evolution are discussed. The modelling of both the charge separation function of the photosystems and the properties of the catalytically active manganese is of current interest from an energy production point of view.
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