title: Resonance Raman characterization of the heme prosthetic group in eosinophil peroxidase.
abstract: The resonance-enhanced Raman spectrum of eosinophil peroxidase (EPO) from horse and human eosinophils is reported. Based upon the spectral energies, distribution and depolarization ratios of the high-frequency skeletal modes and upon the presence of weak bands assignable to vinyl substituent groups, we conclude that the heme prosthetic group is high-spin, 6 coordinate protoporphyrin. The Raman spectrum reveals clear differences from lactoperoxidase (LPO), an enzyme which appears nearly structurally isomorphous by other physical techniques; the data indicate a stronger axial 6th ligand in EPO. Mechanistic implications are discussed in relation to LPO and myeloperoxidase, an enzyme present in neutrophils and monocytes which contains a unique functional active-site chlorin.
mesh_terms: D000818:Animals; D004804:Eosinophils / Q000201:enzymology*; D006418:Heme; D006736:Horses; D007784:Lactoperoxidase; D010544:Peroxidases; D013059:Spectrum Analysis, Raman
chemical_list: D006418:Heme; D007784:Lactoperoxidase; D010544:Peroxidases