Abstract: To unveil the mechanism of fast autooxidation of fish
myoglobins, the effect of temperature on the structural change of tuna
myoglobin was investigated. Purified myoglobin was subjected to
preincubation at 5, 20, 50 and 40oC. Overall helical structural decay
through thermal treatment up to 95oC was monitored by circular
dichroism spectrometry, while the structural changes around the heme
pocket was measured by ultraviolet/visible absorption spectrophotometry.
As a result, no essential structural change of myoglobin
was observed under 30oC, roughly equivalent to their body
temperature, but the structure was clearly damaged at 40oC. The Soret
band absorption hardly differed irrespective of preincubation
temperature, suggesting that the structure around the heme pocket was
not perturbed even after thermal treatment.