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pH- and temperature-dependent denaturation profiles of tuna myoglobin

Nurilmala, Mala, Ushio, Hideki, Ochiai, Yoshihiro
Fisheries science 2018 v.84 no.3 pp. 579-587
absorbance, denaturation, horses, myoglobin, pH, temperature, tuna, wavelengths
Attempts have been made to elucidate the denaturation profiles of tuna myoglobin (Mb) in comparison with horse Mb. Intensive absorbance characterization was carried out for derivatives (deoxy, oxy, met forms) of Mb. The wavelength of the maximum absorbance of tuna Mb was shorter only by 1 nm for deoxy and metMb, while it was 4 nm shorter for the second peak of metMb. Percentage Mb denaturation (PMD) was measured under a combination of pH (5.6, 6.5, 7.4) and temperature (70, 75, 80 °C). Tuna Mb was almost completely denatured even during the initial incubation at 75 and 80 °C at all pHs examined. During the incubation at 70 °C, the PMD values for tuna Mb were 88.5, 52.1, and 67.7% at pH 5.6, 6.5, and 7.4, respectively. The denaturation of tuna Mb proceeded even at 55 °C, but denaturation rates were very slow at pH 6.5. On the other hand, horse Mb was found to be very stable at pH 6.5 and 7.4 at all temperatures examined, except at pH 6.5 and 80 °C. At pH 5.6, the PMD values of horse Mb gradually increased, especially at 75 and 80 °C. These different Mbs showed quite different denaturation profiles.