Complexation of bovine beta-lactoglobulin with 11S protein fractions of soybean (Glycine max) and sesame (Sesamum indicum).

摘要

beta-Lactoglobulin ( beta-Lg) comprises 50% of the whey component of bovine milk. Protein-protein interactions between bovine beta-Lg and 11S protein fractions of soybean and sesame were investigated by turbidity, solubility behaviour and by evaluation of functional properties in the mixed systems. Soy and whey protein ( beta-Lg) showed the formation of soluble complexes. Turbidity and solubility studies showed that the proteins interacted at temp. between 60 and 90 +or- 5 degrees C. Heating a mixture of beta-Lg and 11S proteins of soybean at higher temp. formed soluble complexes with beta-Lg. It also reduced the self aggregation behaviour, especially that of the 11S soy protein fraction. This reduced the precipitation of soy proteins at higher temp. The complex formed was resolved by gel filtration using HPLC. Upon heating beta-Lg at neutral pH, the native dimer started to dissociate into monomers leading to the exposure of previously buried hydrophobic amino acids and the free thiol group. The complex was soluble due to the exposed thiol groups. However, interaction of beta-Lg with sesame 11S protein fractions did not lead to formation of any soluble complexes. The mechanism of interaction indicated that hydrophobic interactions were preferred over disulfide linkages at the high salt concn. of the buffer used. During thermal treatment the molecules became unfolded, leading to exposure of the hydrophobic groups that further enhance the protein-protein interactions that are entropically driven hydrophobic interactions.