Phospholipases as Structural and Functional Probes for Circulating Lipoproteins
In spite of extensive investigations by a variety of physical and chemical techniques, the structural organization of the protein and lipid constituents of the major classes of serum lipoproteins, very low- (VLDL), low- (LDL) and high-density (HDL), remains to be determined (1,2). In the case of phospholipids, their location in the outer polar surface region of the lipoproteins appears to be accepted; yet their mode of interaction with proteins and with the other lipid constituents is essentially unknown. Some theories propose that the polar head groups are involved in electrostatic interactions with particular regions of the polypeptide chains (3), others favor a predominance of hydrophobic interactions between the hydrocarbon chains of phospholipids and the non-polar face of the apolipoproteins (4–6). Even within the framework of current theories on serum lipoprotein structure the role played by the individual phospholipids (phosphatidylcholine, sphingomyelin, phosphatidylethanolamine, etc.) is totally unexplored.
KeywordsCholesteryl Ester Serum Lipoprotein Lipolytic Enzyme Fatty Acid Product Lipid Constituent
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