Can ferric-oxyl excited states explain elongated iron-oxygen bonds in heme peroxidase catalytic intermediates?
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41634046.
- Also identified by DOI 10.1038/s41467-026-69192-8 and PMC identifier 12976261.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The use of X-ray structures to determine and interpret the ferryl iron-oxygen bond order in molecular oxygen-activating heme enzymes has, in the past, been controversial. This has mainly stemmed from the susceptibility of ferryl species to X-ray-induced electronic state changes. In this work we establishe using time-resolved serial femtosecond X-ray crystallography (tr-SFX) on a dye-decolourising peroxidase that the ferryl intermediate species (Compounds I and II) captured following in situ mixing of microcrystals with H<sub>2</sub>O<sub>2</sub> have single, rather than the double bond character expected. X-ray emission validated tr-SFX data with quantum refinement, time-dependent-DFT calculations and QM/MM geometry optimizations together support the concept that the single iron-oxygen bond character is not an indication of ferryl reduction or a protonated form (Fe<sup>IV</sup>-OH) but is instead attributed to the existence of accessible excited states possessing ferric-oxyl (Fe<sup>III</sup>-O<sup>•-</sup>) character. Such states offer insight into the nature of ferryl heme.
Medical subject headings
- Oxygen
- Heme
- Iron
- Peroxidase