Characterisation of the small molecular weight apolipoproteins from pig plasma very low density lipoprotein.

The small molecular weight apolipoproteins of pig very low density lipoprotein were investigated following their separation by gel filtration and ion exchange chromatography. Gel filtration through Sephadex G-200 in 6 M urea, produced essentially the same elution profile to that obtained after filtration of human very low density apolipoprotein. However, separation of the pig Sephadex fraction corresponding to human C proteins on DEAE-cellulose columns revealed the presence of only one major peptide and minor quantities of several others. Some properties of three apparent homogeneous fractions and one heterogeneous DEAE fraction were investigated. Unlike human apoprotein CII apoprotein, none of the pig peptides studied activated cow's milk lipase and sialic acid was not detected in any of the three purified C peptides of pig VLDL. The amino acid compositions of the pig peptides were different to those reported for human C apoproteins. The carboxy terminal residue of the major pig C peptide was shown to be serine. The differences so far revealed between pig and human C peptides need further investigation especially since this animal is regarded as a suitable model for investigating human lipoprotein metabolism and the development of atherosclerosis.