The role of iron-sulfur cluster redox carriers in transforming carbon dioxide

The oxo-acid:ferredoxin oxidoreductase (OFOR) enzyme superfamily represents one of the best examples to study the reversible transformation of CO₂. Members of the family are responsible for both oxidizing oxo-acids such as pyruvate, as in a PFOR, to produce electrons that are taken up in a ferredoxin (Fd) pool, and yield acetyl-CoA. However, OFORs must also operate in the reductive direction, such as the OGOR enzyme that produces oxo-glutarate from CO₂ and succinyl-coA, taking up electrons from Fd proteins. How nature biases oxidation versus reduction is not well understood for the OFOR superfamily. Recently we have found that the role of the Fd redox partner can play a key role in determining the outcomes of the potentially reversible reaction. Here the latest data involving the role of redox potentials, ferredoxin identity, and open questions regarding OFOR mechanism will be presented.