Structural and Functional Changes of Hen's Egg Yolk Low-Density Lipoproteins with Phospholipase A2

Structural and functional changes of hen's egg yolk low-density lipoproteins (LDL) as a result of modifying its phospholipids (PLs) using phospholipase A2 were examined. The 31P NMR spectrum and enzyme hydrolysis profiles revealed that the PLs are more susceptible in LDL complex than in small unilamellar vesicles (SUV) or PLs emulsions, suggesting higher membrane fluidity of LDL and that the interactions of proteins with PLs are not strong. Although the modification of PLs in LDL did not affect the secondary structure of proteins or immunological property of LDL, the emulsions stabilized with the modified LDL showed considerable heat stability. The differences in thermal behavior of modified LDL by DSC analysis suggested the formation of a structurally heat-stable complex of LysoPLs/polypeptides in LDL during heat treatment. The enhancement of PLs−protein interactions in LDL by phospholipase A2 could be responsible for the heat stability of emulsions made from the modified LDL. Keywords: Egg yolk; low-density lipoproteins; phospholipids−protein interaction; emulsion; heat stability; phospholipase A2; structural stability