Resonance Raman characterization of heme Fe(IV)=O groups of intermediates of yeast cytochrome C peroxidase and lactoperoxidase

Resonance Raman Fe(IV)=O stretching vibrations of intermediates of cytochrome c peroxidase and lactoperoxidase are identified on the basis of 18 O-induced frequency shifts. For cytochrome c peroxidase compounds ES a broad Fe(IV)=O peak centered at 753 cm −1 is identified by an 18 O-shift to 725 cm −1 . For lactoperoxidase compound II, a broad feature at 745 cm −1 , identified by spectral subtraction, undergoes an 18 O-induced shift to 712 cm −1 . Previous ferryl heme protein Fe(IV)=O frequencies have been found in the range from 770 to 800 cm −1 . The present Fe(IV)=O frequencies are thus the lowest Fe(IV)=O frequencies reported to date for ferryl (compound II type) heme enzyme intermediates and imply stronger hydrogen bond donation from distal amino acids to the oxo-ferryl group than for previously reported peroxidases. Concomitant with the lowered frequencies is a considerably higher Fe(IV)=O oxygen exchange efficiency with solvent water than previously observed for horseradish peroxidase compound II.