Heme-linked proton dissociation of carbon monoxide complexes of myoglobin and peroxidase.
It was found from spectrophotometric titration and proton balance measurement that the pKa value of a heme-linked protonation group of horseradish ferro-peroxidase C (donor:H2O2 oxidoreductase, EC 1.11.1.7) shifted from 7.25 to 8.25 upon combination with CO. The spectrophotometric titration experiment with myoglobin also revealed the presence of a heme-linked protonation group, the pKa value being 5.57 in myoglobin and 5.67 in the CO-myoglobin complex. It was concluded that the distinct shift of the pKa value in the case of peroxidase was attributable to the presence of a hydrogen bond between the sixth ligand and the distal base. The difference in the strength of such hydrogen bonding between peroxidase and myoglobin was discussed.
D000818:Animals; D001665:Binding Sites; D002248:Carbon Monoxide; D006418:Heme; D006735:Horseradish Peroxidase; D006863:Hydrogen-Ion Concentration; D009132:Muscles; D009211:Myoglobin; D010084:Oxidation-Reduction; D010544:Peroxidases; D011485:Protein Binding; D013053:Spectrophotometry; D014907:Whales
D009211:Myoglobin; D006418:Heme; D002248:Carbon Monoxide; D006735:Horseradish Peroxidase; D010544:Peroxidases