Intermediates involved in the Reduction of SO2: Insight into the mechanism of Sulfite Reductases
Abstract
Sulfite Reductase (SiR) catalyze the reduction of SO32- to H2S in both biosynthetic sulfur assimilation and dissimilation of sulfate. The mechanism of the 6e-/6H+ reduction of SO32- at the siroheme cofactor is debated and the proposed intermediates involved in this 6e- reduction are yet to be spectroscopically characterized. The reaction of SO2 with a ferrous iron porphyrin is investigated and two intermediates are trapped and characterized; an initial Fe(III)-SO22- species which undergoes proton assisted S-O bond cleavage to form an Fe(III)-SO species. These species are characterized using a combination of resonance Raman (with 34S labelled SO2), EPR and DFT calculations. The results obtained help reconciliate the different proposed mechanisms for SiR.
- This article is part of the themed collection: CC 60th Anniversary Authors Collection