TY - JOUR
T1 - Formation of compound I in the reaction of native myoglobins with hydrogen peroxide
AU - Egawa, Tsuyoshi
AU - Shimada, Hideo
AU - Ishimura, Yuzuru
PY - 2000/11/10
Y1 - 2000/11/10
N2 - Reaction of ferric native myoglobin (Mb) with hydrogen peroxide (H2O2) was studied by the aid of stopped-flow rapid-scan spectrophotometry. In contrast to the results in previous studies where compound I was reported to be undetectable, both sperm whale and horse heart metmyoglobins (metMbs) formed a significant quantity of compound I, an oxoferryl porphyrln π-cation radical (Por+-Fe (IV)(O)), during their reactions with H2O2. With both kinds of Mbs, formation of compound I was more clearly observed in D2O than in H2O. The compound thus formed was capable of performing monooxygenation of thioanisole to methyl phenyl sulfoxide and a 2-electron oxidation of H2O2 giving O2 and H2O as products. It was also converted into ferryl myoglobin (Por-Fe (IV)(O)-globin+) spontaneously. Rate constants for these reactions and that for a direct conversion of metMb to ferryl Mb through the homolysis of H2O2 were determined. These results established unambiguously that native metMb can form both compound I and ferryl Mb upon reaction with H2O2 and that these high valent iron compounds serve as essential intermediates in Mb-assisted peroxidative reactions. The observed deuterium effect on the apparent stability of compound I was attributable to that effect on the hydrogen abstraction step in the 2-electron oxidation of H2O2 by compound I.
AB - Reaction of ferric native myoglobin (Mb) with hydrogen peroxide (H2O2) was studied by the aid of stopped-flow rapid-scan spectrophotometry. In contrast to the results in previous studies where compound I was reported to be undetectable, both sperm whale and horse heart metmyoglobins (metMbs) formed a significant quantity of compound I, an oxoferryl porphyrln π-cation radical (Por+-Fe (IV)(O)), during their reactions with H2O2. With both kinds of Mbs, formation of compound I was more clearly observed in D2O than in H2O. The compound thus formed was capable of performing monooxygenation of thioanisole to methyl phenyl sulfoxide and a 2-electron oxidation of H2O2 giving O2 and H2O as products. It was also converted into ferryl myoglobin (Por-Fe (IV)(O)-globin+) spontaneously. Rate constants for these reactions and that for a direct conversion of metMb to ferryl Mb through the homolysis of H2O2 were determined. These results established unambiguously that native metMb can form both compound I and ferryl Mb upon reaction with H2O2 and that these high valent iron compounds serve as essential intermediates in Mb-assisted peroxidative reactions. The observed deuterium effect on the apparent stability of compound I was attributable to that effect on the hydrogen abstraction step in the 2-electron oxidation of H2O2 by compound I.
UR - http://www.scopus.com/inward/record.url?scp=0034634543&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034634543&partnerID=8YFLogxK
U2 - 10.1074/jbc.M004026200
DO - 10.1074/jbc.M004026200
M3 - Article
C2 - 10945982
AN - SCOPUS:0034634543
SN - 0021-9258
VL - 275
SP - 34858
EP - 34866
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 45
ER -