ISOELECTRIC HETEROGENEITY OF THE COFACTOR PROTEIN FOR LIPOPROTEIN-LIPASE IN HUMAN-BLOOD PLASMA

Several of the protein componets of lipoproteins in mammalian blood plasma exhibit charge polymorphism (1-7). In some cases, polymorphism in gel electrophoretograms is clearly evident only upon isoelectric focusing (2,3,6,7). In the case of the human apolipoprotein R-ala (apo C-III), variable sialylation accounts for the polymorphism (4,5), but in other cases the basis for polymorphism is unknown. Deficiency of one of the polymorphic components of the arginine-rich apolipoprotein (apo E) is associated with one genetically determined human hyperlipoproteinemia, familial dysbetalipoproteinemia (6,7). We have isolated a new component of the C" group of apoproteins of human VLDL and have found it to be an isoelectric variant of the cofactor protein for lipoprotein lipase (R-glu; apo C-II). © 1979."