Effect of Retinol and Fatty Acid Binding by Bovine beta-Lactoglobulin on its Resistance to Trypsin Digestion

beta-Lactoglobulin has been reported to be quite resistant to proteolysis by digestive enzymes. In this work, the effect of the binding of retinol and fatty acids to beta-lactoglobulin on the resistance of this protein to trypsin degradation has been studied. When delipidated beta-lactoglobulin and beta-lactoglobulin with bound retinol were treated with trypsin and subjected to HPLC gel filtration, no major differences were found in the degradation products. However, proteolysis decreased when beta-lactoglobulin contained bound palmitic acid. After 4 h of trypsin incubation, less than 30% of delipidated beta-lactoglobulin or beta-lactoglobulin with bound retinol remained undegraded, while 60% of beta-lactoglobulin with bound fatty acids was still intact. These results indicate that the binding of fatty acids to beta-lactoglobulin increases its conformational stability to tryptic degradation.