Comparison of the ability to bind lipids of beta-lactoglobulin and serum albumin of milk from ruminant and non-ruminant species.

The interaction of sheep, horse, pig, human and guinea-pig whey proteins with fatty acids has been studied. Using gel filtration and autoradiography, it was found that sheep beta-lactoglobulin and serum albumin from all species had the ability to bind fatty acids in vitro. Sheep beta-lactoglobulin, isolated from milk, had approximately 0.5 mol fatty acids bound per mol monomer protein, and albumin from sheep, horse and pig contained approximately 4.5, 2.9 and 4.7 mol fatty acids/mol protein respectively. However, beta-lactoglobulin from horse and pig milk had neither fatty acids physiologically bound nor the ability to bind them in vitro. Albumin was the only whey protein detected with bound fatty acids in these species as well as in human and guinea pig. This suggests that the ability of ruminant beta-lactoglobulin to bind fatty acids was not shared by the same protein of non-ruminants.