Isotopic Effect on the Kinetic of Thermal Denaturation of Ceruloplasmin
2014
The kinetics of thermal denaturation of ceruloplasmin in water and in water with different percentage of D20 in the temperature range 25 - 85 °C, following the optical density change of the 610 nm charge transfer band of the protein has been investigated.A temperature Tₜ ≃ 65 °C above which an irreversible denaturation process of the protein active site takes place has been found.The kinetics of the denaturation process of the protein are fitted by two first order reactions, which have been assigned to a different thermal denaturation behaviour of the two Cu²⁺ type I sites existing in the protein. Addition of D₂O to the protein solution affects the two kinetics in a different way, i.e. the rate of one of them is increased whilst that of the other is decreased.The different effect of D₂O on the kinetics of disruption of the two copper sites is discussed in terms of different location and degree of hydrophobicity of the two Cu²⁺ type I sites.
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