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Updated: May 25, 2026
05:47
Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts
Published on: August 7, 2018
Light-driven oxygen production from superoxide by Mn-binding bacterial reaction centers
James P Allen1, Tien L Olson, Paul Oyala
1Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604, USA. JAllen@asu.edu
Summary
Ancient bacteria evolved oxygenic photosynthesis by modifying reaction centers to bind manganese. These modified centers efficiently convert superoxide to oxygen, offering a survival advantage before complex water-splitting evolved.
Area of Science:
- Biochemistry
- Evolutionary Biology
- Photosynthesis Research
Background:
- The evolution of oxygenic photosynthesis by early phototrophs remains a key question.
- Oxygenic photosynthesis led to a significant increase in atmospheric oxygen.
- Photosystem II in modern organisms contains a manganese cofactor essential for water oxidation.
Purpose of the Study:
- To investigate the enzymatic function of modified anoxygenic bacterial reaction centers capable of binding manganese.
- To determine if these modified centers could perform light-driven enzymatic reactions relevant to early Earth conditions.
- To assess the stability and efficiency of these manganese-binding reaction centers.
Main Methods:
- Modification of anoxygenic photosynthetic bacterial reaction centers to bind a redox-active manganese (Mn) cofactor.
- Assay of light-driven enzymatic activity, specifically the conversion of superoxide to molecular oxygen.
- Determination of kinetic parameters (kcat and Km) for the observed enzymatic activity.
- Assessment of the stability of modified reaction centers in the presence and absence of bound Mn under illumination.
Main Results:
- Manganese-binding reaction centers exhibit light-driven enzymatic activity, converting superoxide to oxygen with a kcat of approximately 1 s(-1).
- The enzyme displays a Km of 35-40 μM for superoxide, comparable to Mn-superoxide dismutase.
- Modified reaction centers require bound manganese for stability in the light, unlike wild-type centers.
- This suggests a potential intermediate step in the evolution of photosynthesis.
Conclusions:
- Modified anoxygenic reaction centers with bound manganese possess a light-driven enzymatic function to convert superoxide to oxygen.
- This enzymatic capability and enhanced stability would have provided a selective advantage to primitive phototrophs.
- These findings offer insights into the evolutionary transition towards oxygenic photosynthesis and the development of the complex Mn(4)Ca cluster.
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