XFEL Crystal Structures of Peroxidase Compound II

Oxygen activation in all heme enzymes requires the formation of high oxidation states iron, usually referred to as ferryl heme. There are two known intermediates: Compound I and II. The nature heme—and whether it is an FeIV=O or FeIV-OH species—is important for controlling reactivity across groups enzymes. most recent evidence indicates that unprotonated species. For II, not unambiguously established. Here, we report 1.06 Å 1.50 crystal structures II intermediates cytochrome c peroxidase (CcP) ascorbate (APX), collected using X-ray free electron laser at SACLA. reveal differences between peroxidases. iron-oxygen bond length CcP (1.76 Å) notably shorter than APX (1.87 Å). results indicate species finely tuned closely related We propose this fine-tuning linked functional need proton delivery