title: Oxygen-17 nuclear magnetic resonance spectroscopic studies of carbonmonoxyperoxidases.
abstract: We have obtained oxygen-17 (17O) nuclear magnetic resonance (NMR) spectra of C17O ligands bound to ferrous horseradish peroxidase isozyme A, isozyme C, and ferrous chloroperoxidase, as a function of pH. Our results show that the peroxidases exist in two distinct states, the acidic and alkaline forms, which undergo reversible acid-base-induced transitions characterized by a single pK value. The two forms are characterized spectroscopically in much the same way in all three proteins, suggesting a similar structural origin for the transition process. In particular, the 17O NMR signal of the acidic form is approximately 7 ppm more shielded than that of the alkaline form, and the CO ligand in the acidic form appears to have a smaller 17O nuclear quadrupole coupling constant than that of the alkaline form. We have also obtained the pK values and exchange rates for all three peroxidases. The results indicate that a similar structural change may be involved in the transition process in all three peroxidases.
authors.affiliation: School of Chemical Sciences, University of Illinois, Urbana-Champaign 61801.
authors.forename: H C
authors.initials: HC
authors.lastname: Lee
authors.forename: K
authors.initials: K
authors.lastname: Cummings
authors.forename: K
authors.initials: K
authors.lastname: Hall
authors.forename: L P
authors.initials: LP
authors.lastname: Hager
authors.forename: E
authors.initials: E
authors.lastname: Oldfield
mesh_terms: D002248:Carbon Monoxide / Q000378:metabolism*; D002711:Chloride Peroxidase / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D010103:Oxygen Isotopes; D010544:Peroxidases / Q000378:metabolism*; D011485:Protein Binding
chemical_list: D007527:Isoenzymes; D010103:Oxygen Isotopes; D002248:Carbon Monoxide; D006735:Horseradish Peroxidase; D010544:Peroxidases; D002711:Chloride Peroxidase