Formation of long-lived radicals on proteins by radical transfer from heme enzymes--a common process?
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Formation of long-lived radicals on proteins by radical transfer from heme enzymes--a common process? / Ostdal, H; Andersen, H J; Davies, Michael Jonathan.
In: Archives of Biochemistry and Biophysics, Vol. 362, No. 1, 01.02.1999, p. 105-12.Research output: Contribution to journal › Journal article › peer-review
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TY - JOUR
T1 - Formation of long-lived radicals on proteins by radical transfer from heme enzymes--a common process?
AU - Ostdal, H
AU - Andersen, H J
AU - Davies, Michael Jonathan
N1 - Copyright 1999 Academic Press.
PY - 1999/2/1
Y1 - 1999/2/1
N2 - Incubation of Fe(III)myoglobin (Fe(III)Mb) with H2O2 in the presence of bovine serum albumin (BSA) has been shown previously to give albumin-derived radicals as a result of radical transfer from myoglobin to BSA. In this study the occurrence of similar processes with peroxidases has been investigated using horseradish peroxidase (HRP)/H2O2, in the presence and absence of added tyrosine. Incubation of HRP with H2O2 and bovine or human serum albumins, in the presence and absence of tyrosine, gave long-lived albumin-derived radicals as detected by EPR spectroscopy. Evidence has been obtained for these albumin radicals being located on buried tyrosine residues on the basis of blocking experiments. The effect of protein conformation on radical transfer has been investigated using partial proteolytic digestion prior to protein oxidation. With HRP/H2O2/BSA and Fe(III)Mb/H2O2/BSA increased radical concentrations were observed after limited digestion, although this effect was less marked with the HRP/H2O2/BSA system than with Fe(III)Mb/H2O2/BSA, consistent with different modes of radical transfer. More extensive digestion of BSA decreased the radical concentration to levels below those detected with native albumin, indicating that the tertiary structure of the target protein plays an important role in determining the rate of radical transfer and/or the stability of the resultant species. These results are consistent with a mechanism for the HRP/H2O2/no free tyrosine system involving radical transfer to the albumin via the heme edge of the peroxidase. In contrast, albumin radical formation by the HRP/H2O2/free tyrosine system was only marginally affected by proteolysis, consistent with free tyrosine phenoxyl radicals being the mediators of radical transfer, without significant protein-protein interaction. These protein-to-protein radical transfer reactions may have important consequences for understanding protein oxidation in biological systems.
AB - Incubation of Fe(III)myoglobin (Fe(III)Mb) with H2O2 in the presence of bovine serum albumin (BSA) has been shown previously to give albumin-derived radicals as a result of radical transfer from myoglobin to BSA. In this study the occurrence of similar processes with peroxidases has been investigated using horseradish peroxidase (HRP)/H2O2, in the presence and absence of added tyrosine. Incubation of HRP with H2O2 and bovine or human serum albumins, in the presence and absence of tyrosine, gave long-lived albumin-derived radicals as detected by EPR spectroscopy. Evidence has been obtained for these albumin radicals being located on buried tyrosine residues on the basis of blocking experiments. The effect of protein conformation on radical transfer has been investigated using partial proteolytic digestion prior to protein oxidation. With HRP/H2O2/BSA and Fe(III)Mb/H2O2/BSA increased radical concentrations were observed after limited digestion, although this effect was less marked with the HRP/H2O2/BSA system than with Fe(III)Mb/H2O2/BSA, consistent with different modes of radical transfer. More extensive digestion of BSA decreased the radical concentration to levels below those detected with native albumin, indicating that the tertiary structure of the target protein plays an important role in determining the rate of radical transfer and/or the stability of the resultant species. These results are consistent with a mechanism for the HRP/H2O2/no free tyrosine system involving radical transfer to the albumin via the heme edge of the peroxidase. In contrast, albumin radical formation by the HRP/H2O2/free tyrosine system was only marginally affected by proteolysis, consistent with free tyrosine phenoxyl radicals being the mediators of radical transfer, without significant protein-protein interaction. These protein-to-protein radical transfer reactions may have important consequences for understanding protein oxidation in biological systems.
KW - Animals
KW - Cattle
KW - Electron Spin Resonance Spectroscopy
KW - Free Radicals
KW - Hemeproteins
KW - Horseradish Peroxidase
KW - Horses
KW - Humans
KW - Hydrogen Peroxide
KW - Metmyoglobin
KW - Oxidation-Reduction
KW - Pronase
KW - Protein Structure, Secondary
KW - Protein Structure, Tertiary
KW - Serum Albumin, Bovine
KW - Tyrosine
U2 - 10.1006/abbi.1998.0988
DO - 10.1006/abbi.1998.0988
M3 - Journal article
C2 - 9917334
VL - 362
SP - 105
EP - 112
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
SN - 0003-9861
IS - 1
ER -
ID: 138282907