No abstract

No abstract

No abstract

To probe the identity of the active site hemetype prooshetic group ofmyeloperoxidase, whose (5,6,9,10), the spectroscopic properties of analogous derivatives with the same oxidation and ligation states can be used to probe the similarity or difference in their prosthetic group structures. MCD spectral comparison between myoglobin reconstituted with Spirographis heme (Spirographis Mb) and MPO in this study reveals considerable spectral similarities between parallel derivatives of these two proteins, especially in the ferric high-spin native form and the ferrous low-spin complexes. Given the repeatedly demonstrated ability of MCD spectroscopy to identify or distinguish two apparently similar chromophores more definitively than electronic absorption spectroscopy (18-20), the present finding provides strong support for a formyl-substituted porphyrin as the structure of the prosthetic group macrocycle of MPO. EXPERIMENTAL PROCEDURES Spirographis Mb was prepared from horse heart apo-Mb and Spirographis heme as described by Sono and Asakura (16,21,22). MPO was purified from bovine spleen as described (23). Metal-free trans-octaethylchlorin (GEC) was obtained by a published method (24) and metallated to produce Fe-(OEC)Cl using a modification (25) of the direct iron insertion method (26). All chemicals were reagent grade and were obtained from Aldrich or Sigma. N-Methylimidazole and benzene were further purified by distillation.The reduced pyridine hemochromogen [the ferrous bis(pyridine) adduct] of Spirographis heme (and Mb) or MPO was generated by dissolving the heme or diluting the concentrated protein stock solution into a pyridine/NaOH solution [25-35% pyridine (vol/vol) and 0

No abstract