Isolation and characterization of polymorphic forms of porcine apoC-II by chromatofocusing

Chromatofocusing, which separates proteins on the basis of their different isoelectric points, was used to isolate isoforms of apoC-II from porcine very low density lipoproteins. This method was found to be time-saving and the yield of protein recovery was high. With chromatofocusing, three polypeptides were obtained which were characterized by amino acid analysis, double immunodiffusion, and by their ability to activate bovine milk lipoprotein lipase. The three polypeptides had the same amino acid composition, gave a reaction of identity against a monospecific antiserum to porcine apoC-II, but had different isoelectric points between pH 4.8 and 4.4. They all enhanced the activity of lipoprotein lipase, but to a lesser degree than native porcine serum. There was no indication of the existence of apolipoproteins that correspond to human apoC-III polypeptides.