Electron paramagnetic resonance spectroscopy of lactoperoxidase complexes: clarification of hyperfine splitting for the NO adduct of lactoperoxidase
Electron paramagnetic resonance (EPR) studies of the nitrosyl adduct of ferrous lactoperoxidase (LPO) confirm that the fifth axial ligand in LPO is bound to the iron via a nitrogen atom. Complete reduction of the ferric LPO sample is required in order to observe the nine-line hyperfine splitting in the ferrous LPO/NO EPR spectrum. The ferrous LPO/NO complex does not exhibit a pH or buffer system dependence when examined by EPR. Interconversion of the ferrous LPO/NO complex and the ferric LPO/NO/sub 2//sup -/ complex is achieved by addition of the appropriate oxidizing or reducing agent. Characterization of the low-spin LPO/NO/sub 2//sup -/ complex by EPR and visible spectroscopy is reported. The pH dependence of the EPR spectra of ferric LPO and ferric LPO/CN/sup -/ suggests that a high-spin anisotrophic LPO complex is formed at high pH and an acid-alkaline transition of the protein conformation near the heme site does occur in LPO/CN/sup -/. The effect of tris(hydroxymethyl)aminomethane buffer on the LPO EPR spectrum is also examined.
- Research Organization:
- Univ. of Iowa, Iowa City
- OSTI ID:
- 5589154
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:22; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ABSORPTION SPECTRA
ADDUCTS
ANISOTROPY
BIOLOGICAL EFFECTS
CARBOHYDRATES
CHALCOGENIDES
DISACCHARIDES
ELECTRON SPIN RESONANCE
ENZYMES
GLUCOPROTEINS
HYPERFINE STRUCTURE
IRON COMPOUNDS
LACTOSE
LIGANDS
MAGNETIC RESONANCE
NITRITES
NITROGEN COMPOUNDS
NITROGEN OXIDES
OLIGOSACCHARIDES
ORGANIC COMPOUNDS
OXIDES
OXIDOREDUCTASES
OXYGEN COMPOUNDS
PEROXIDASES
PH VALUE
PROTEINS
RESONANCE
SACCHARIDES
SPECTRA
TRANSITION ELEMENT COMPOUNDS