Autoxidation of myoglobin from bigeye tuna fish ( Thunnus obesus)

• Published in: Biochimica et biophysica acta Vol. 1038; no. 1; pp. 23 - 28
• Main Authors: Kitahara, Yoshiro, Matsuoka, Ariki, Kobayashi, Nagao, Shikama, Keiji
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 29.03.1990
• Subjects: Animals; Autoxidation; chemical kinetics; Circular Dichroism; Fishes - physiology; Heme; Hydrogen-Ion Concentration; Kinetics; Marine; muscles; Muscles - analysis; Myoglobin; Myoglobin - isolation & purification; myoglobins; oxidation; Oxidation-Reduction; skeletal muscle; Solubility; stability; Structure-Activity Relationship; T. obesus; Thunnus obesus; Tuna - physiology; Water; Myoglobin; Autoxidation; T. obesus; MbO 2; metMb; Circular dichroism
• DOI: 10.1016/0167-4838(90)90005-Z
• ISSN: 0167-4838; 0006-3002

Native oxymyoglobin (MbO 2) was isolated directly from the skeletal muscle of bigeye tuna ( Thunnus obesus) with complete separation from metmyoglobin (metMb) on a CM-cellulose column. It was examined for its stability properties over a wide range of pH values (pH 5–12) in 0.1 M buffer at 25°C. When compared with sperm whale MbO 2 as a reference, the tuna MbO 2 was found to be much more susceptible to autoxidation. Kinetic analysis has revealed that the rate constant for a nucleophilic displacement of O 2 − from MbO 2 by an entering water molecule is 10-times higher than the corresponding value for sperm whale MbO 2. The magnitude of the circular dichroism of bigeye tuna myoglobin at 222 nm was comparable to that of sperm whale myoglobin, but its hydropathy profile revealed the region corresponding to the distal side of the heme iron to be apparently less hydrophobic. The kinetic simulation also demonstrated that accessibility of the solvent water molecule to the heme pocket is clearly a key factor in the stability properties of the bound dioxygen.