Interaction of bovine αα-lactalbumin with fatty acids as determined by partition equilibrium and fluorescence spectroscopy

The interaction of bovine holo- and apo- αα-lactalbumin with fatty acids was studied using a partition equilibrium technique and fluorescence spectroscopy. Using there techniques, bovine holo- αα-lactalbumin was found to be unable to bind fatty acids. Gas chromatography analysis also did not reveal and fatty acids bound to bovine αα-lactalbumin that had been isolated using non denaturing conditions. The partition equilibrium showed that bovine apo- αα-lactalbumin has one binding site for fatty acids, having association constants of 4.6×106 and 5.4×105 m−1 for oleic and palmitic acids, respectively. The binding of bovine apo- αα-lactalbumin studied by fluorescence spectroscopy also showed the existence of a binding site for oleic acid with a binding constant of 3.3×106 m−1, but the binding parameters could not be estimated for palmitic acid due to low fluorescence enhancement. These results demonstrate that the conformational change induced in α-lactalbumin by the removal of calcium enables the protein to interact with fatty acids.