Sep 26, 1997

A metalloradical mechanism for the generation of oxygen from water in photosynthesis

Science
Curtis W Hoganson, G T Babcock

Abstract

In plants and algae, photosystem II uses light energy to oxidize water to oxygen at a metalloradical site that comprises a tetranuclear manganese cluster and a tyrosyl radical. A model is proposed whereby the tyrosyl radical functions by abstracting hydrogen atoms from substrate water bound as terminal ligands to two of the four manganese ions. Molecular oxygen is produced in the final step in which hydrogen atom transfer and oxygen-oxygen bond formation occur together in a concerted reaction. This mechanism establishes clear analogies between photosynthetic water oxidation and amino acid radical function in other enzymatic reactions.

Mentioned in this Paper

Manganese
Dioxygen
Photosynthetic Reaction Centers
Fast Electrons
Hydrogen
Oxygen Evolving Activity
Oxidation
Oxidation-Reduction
Manganese Measurement
Photosynthetic Reaction Center Complex Proteins

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