title: Chloroperoxidase: P-450 type absorption in the absence of sulfhydryl groups.
abstract: The oxidation state of the two half-cystine residues in the native ferric form of chloroperoxidase and in the reduced ferrous chloroperoxidase has been examined in order to evaluate the role of sulfhydryl groups as determinants of P-450 type spectra. Mössbauer and optical spectroscopy studies indicate that the ferrous forms of P-450cam and chloroperoxidase have very similar or identical heme environments. Model studies have suggested that sulfhydryl groups may function as axial ligands for developing P-450 character. However, chemical studies involving both sulfhydryl reagents and amperometric titrations show that neither the ferric nor the chemically produced ferrous forms of chloroperoxidase contain a sulfhydryl group. These results rule out the hypothesis that sulfhydryl groups are unique components for P-450 absorption characteristics. The optical and electron paramagnetic resonance (EPR) spectra of the nitric oxide complex of chloroperoxidase have been obtained and compared to those of myoglobin, hemoglobin, and cytochrome c and horseradish peroxidase. The EPR spectrum of the NO-ferrous chloroperoxidase complex, which is similar to that of cytochrome P-450cam, does not show the extra nitrogen hyperfine structure which appears to be characteristic of those hemoproteins which have a nitrogen atom as an axial heme ligand.
mesh_terms: D055598:Chemical Phenomena; D002621:Chemistry; D002711:Chloride Peroxidase; D003577:Cytochrome P-450 Enzyme System; D004578:Electron Spin Resonance Spectroscopy; D005290:Ferric Compounds; D005296:Ferrous Compounds; D006420:Hemeproteins; D006735:Horseradish Peroxidase; D008024:Ligands; D009686:Nuclear Physics; D010084:Oxidation-Reduction; D010544:Peroxidases; D013053:Spectrophotometry; D013056:Spectrophotometry, Ultraviolet; D013057:Spectrum Analysis; D013438:Sulfhydryl Compounds
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D006420:Hemeproteins; D008024:Ligands; D013438:Sulfhydryl Compounds; D003577:Cytochrome P-450 Enzyme System; D006735:Horseradish Peroxidase; D010544:Peroxidases; D002711:Chloride Peroxidase