Hydrogenation of plasma lipoproteins by a water-soluble catalyst; its use as a structural probe

Hydrogenation of double bonds of fatty acyl chains in the lipids of individual, intact plasma lipoproteins has been accomplished using a water-soluble, homogenous catalyst. Up to 40% of the double bonds can be hydrogenated. The pattern of hydrogenation is similar for each of the lipoprotein fractions; the phospholipids are most extensively hydrogenated but small amounts of cholesteryl ester and triacylglycerol are also hydrogenated. This results is consistent with a surface location of phospholipids and with the majority of the apolar lipids being in a hydrophobic inner core since the catalyst was shown not to be specific for an individual lipid class. It also suggests the some cholesteryl ester and triacylglycerol may be near the lipoprotein surface, accessible to the catalyst. If this is the case, it is speculated that the known exchange of these neutral lipids between the lipoprotein classes and their degradation by lipolytic enzymes may thus be facilitated.