Relationship between oxygen affinity and autoxidation of myoglobin.
Studies using myoglobins reconstituted with a variety of chemically modified heme cofactors revealed that the oxygen affinity and autoxidation reaction rate of the proteins are highly correlated to each other, both decreasing with decreasing the electron density of the heme iron atom. An Fe(3+)-O(2)(-)-like species has been expected for the Fe(2+)-O(2) bond in the protein, and the electron density of the heme iron atom influences the resonance process between the two forms. A shift of the resonance toward the Fe(2+)-O(2) form results in lowering of the O(2) affinity due to an increase in the O(2) dissociation rate. On the other hand, a shift of the resonance toward the Fe(3+)-O(2)(-)-like species results in acceleration of the autoxidation through increasing H(+) affinity of the bound ligand.
Department of Chemistry, University of Tsukuba, Tsukuba 305-8571, Japan.
Tomokazu
T
Shibata
Daichi
D
Matsumoto
Ryu
R
Nishimura
Hulin
H
Tai
Ariki
A
Matsuoka
Satoshi
S
Nagao
Takashi
T
Matsuo
Shun
S
Hirota
Kiyohiro
K
Imai
Saburo
S
Neya
Akihiro
A
Suzuki
Yasuhiko
Y
Yamamoto
D000818:Animals; D006418:Heme / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D009211:Myoglobin / Q000737:chemistry / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet; D014907:Whales
D008024:Ligands; D009211:Myoglobin; D006418:Heme; D010100:Oxygen