Studies on the composition and structure of plasma lipoproteins. Distribution of lipoprotein families in major density classes of normal human plasma lipoproteins.

Abstract To account for the protein heterogeneity of lipoprotein preparations isolated by ultracentrifugal or precipitation techniques, we have proposed a classification system [P. Alaupovic et al., Circulation, 30, Suppl. III (1964) 1; P. Alaupovic, Prog. Biochem. Pharmacol., 4 (1968) 91; P. Alaupovic et al., Expo. Annu. Biochim. Med., 31 (1972)] of plasma lipoproteins based on apolipoproteins as the only distinct chemical components for the differentiation of lipoprotein families. At the present time this concept recognizes the existence of three lipoprotein families, each of which is characterized by the exclusive presence of a single apolipoprotein: lipoprotein family A (LP-A) is characterized by the presence of apolipoprotein A (ApoA), lipoprotein family B (LP-B) by apolipoprotein B (ApoB) and lipoprotein family C (LP-C) by apoliprotein C (ApoC). The qualitative distribution of lipoprotein families in normal human plasma very low density lipoproteins (VLDL, d The LP-A and LP-C families were detected in all lipoprotein density classes; the LP-B family was also present in all classes except the HDL3. Results of the immunological and electrophoretic experiments supported the existence of lipoprotein families as the basic components of plasma lipoprotein system and indicated that lipoprotein families exist above a density range of approximately 1.006-1.019 g/ml as individual separable entities, while at densities less than this range lipoprotein families are present primarily as associations.