Comparative study on heat stability of camel and bovine apo and holo alpha-lactalbumin.

The stability of camel alpha-lactalbumin (alpha-la) against heat denaturation was measured, using circular dichroism (CD) and fluorescence spectroscopy, as well as differential scanning calorimetry (DSC). The experiments were performed in the presence of saturating concentrations of calcium as well as in the presence of EDTA, yielding to the apo form of alpha-la. The change in heat capacity (DeltaCp) suggests a greater contribution of hydrophobic interactions to the stability of holo camel alpha-la than in its bovine counterpart. Overall the results obtained in this study suggest a greater stability of camel alpha-la than the bovine protein in both holo and apo states. Also CD experiments showed similar secondary structure for camel and bovine alpha-la and secondary structure of camel alpha-la was better preserved than that of bovine alpha-la during heat denaturation. The differences in thermal stability between the proteins from two species can be primarily ascribed to the difference in the quantity of hydrophobic interactions involved in their folding.