Thermostabilization of Ovotransferrin by Anions for Pasteurization of Liquid Egg White
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The effects of anions on the thermostability of ovotransferrin (oTf) were investigated. The temperature, <I>T<SUB>m</SUB></I>, causing aggregation of oTf was measured in the presence or absence of anions, and the denaturation temperature, <I>T<SUB>m</SUB></I><SUP><I>DSC</I></SUP>, was also determined by differential scanning calorimetry (DSC) in the presence of the citrate anion. We found that some anions (phosphate, sulfate and citrate) raised temperature <I>T<SUB>m</SUB></I> of oTf by about 5–7 °C. However, neither sodium chloride nor sodium bicarbonate raised <I>T<SUB>m</SUB></I> by that much. Temperature <I>T<SUB>m</SUB></I> was increased by increasing the concentration of the citrate anion, and was in good agreement with denaturation temperature <I>T<SUB>m</SUB></I><SUP><I>DSC</I></SUP>, suggesting that denaturation of the oTf molecules resulted in aggregation of oTf. We also demonstrated that the anions, especially sulfate, repressed the heat-aggregation of liquid egg white.<BR>The Van't Hoff plot from the <I>T<SUB>m</SUB></I> and Δ<I>H<SUB>d</SUB></I> values revealed that two anion-binding sites were concerned with heat stabilization. These binding sites may have been concerned with sulfate binding (not bicarbonate binding) that is found in the crystal structure of apo-form of oTf, since the bicarbonate anion did not raise <I>T<SUB>m</SUB></I>.
- Agricultural and Biological Chemistry
Agricultural and Biological Chemistry 70(8), 1839-1845, 2006-08-23
Japan Society for Bioscience, Biotechnology, and Agrochemistry