The Online Metabolic and Molecular Bases of Inherited Disease > 114: Introduction: Structure and Metabolism of Plasma Lipoproteins

Although it was appreciated at the turn of the century that the lipids of plasma are solubilized by protein,1 it was another 28 years before the first lipoproteins, high-density lipoproteins (HDL), were isolated.2 During the comprehensive efforts to isolate human plasma proteins during World War II, lipoproteins of low density and β electrophoretic mobility were clearly identified and separated from HDL with α mobility.3 Within the next decade, the major antigenic determinants of α and β lipoproteins were shown to be distinct.4,5 Studies of their hydrodynamic behavior demonstrated the existence of the larger, less dense, very low density lipoproteins (VLDL) and intermediate density lipoproteins (IDL);6 it was established that a strongly antigenic protein was common to these lipoproteins and low density lipoproteins (LDL).7 The presence of glutamic acid as the principal N-terminus in LDL8,9 and one of several in VLDL10 gave chemical support to the concept that one protein, distinct from the principal proteins in HDL, is virtually the only apolipoprotein in LDL and is present in significant amounts with other apolipoproteins in VLDL. This common protein constituent of LDL and its lipoprotein precursors was termed “apolipoprotein (apo) B” to distinguish it from the protein moiety of HDL (apo A) and the newly recognized proteins of VLDL (apo C).