Manganese catalase Reaction mechanism

The importance of reactions 1-3 in the biosphere is clear. However, relatively little is known about the catalytic mechanisms of these reactions, particularly reactions 2 and 3. In order to better understand the catalytic mechanisms of these enzymes, it is important to establish the correlation between metal site structure and enzymatic function. X-ray absorption spectroscopy is one of the premier tools for determining the local structural environment of metalloprotein metal sites. In the following, we summarize our results using X-ray absorption spectroscopy to characterize the structure of the Mn active site environments in manganese catalase and in the OEC and show how these structural results can be used to deduce details of the catalytic mechanism of these enzymes. 

The Sq -> S2 reaction involves 0x0 (hydroxo) bridge formation between Mn ions. The PSII manganese cluster also exhibits a catalase activity. It vigorously disprOTortionates added H2O2 in the dark following formation of the So state by a single flash. The mechanism involves initial 2e" reduction S2 ->Sq with O2 formation followed by reoxidation to the So state with H2O release fScheme IV This reaction does not occur if Mn is removed or if me Mn cluster is destroyed. 

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