title: The formation of ferric haem during low-temperature photolysis of horseradish peroxidase Compound I.
abstract: Illumination at low temperature of the peroxide compound of horseradish peroxidase (HRP-I) causes partial conversion of the haem electronic structure from a ferryl-porphyrin radical species into a low-spin ferric state. Magnetic-c.d. (m.c.d.) and e.p.r. spectral features of the photolysis product are almost identical with those of the alkaline form of ferric HRP, proposed on the basis of its near-i.r. m.c.d. spectrum to be a Fe(III)-OH species. The ferric product of HRP-I photolysis also contains free-radical e.p.r. signals. Conversion of HRP-I into the Fe(III)-OH species, which requires transfer of a proton and two electrons from the protein, is shown to be a two-step process.
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich, U.K.
authors.forename: N
authors.initials: N
authors.lastname: Foote
authors.forename: P M
authors.initials: PM
authors.lastname: Gadsby
authors.forename: M J
authors.initials: MJ
authors.lastname: Berry
authors.forename: C
authors.initials: C
authors.lastname: Greenwood
authors.forename: A J
authors.initials: AJ
authors.lastname: Thomson
mesh_terms: D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D006418:Heme / Q000032:analysis*; D006735:Horseradish Peroxidase; D007527:Isoenzymes; D008956:Models, Chemical; D010544:Peroxidases; D010782:Photolysis; D013053:Spectrophotometry; D013696:Temperature
chemical_list: D007527:Isoenzymes; D006418:Heme; D006735:Horseradish Peroxidase; D010544:Peroxidases