The Distribution of J Blood‐Group Activity on Lipoprotein and Protein Fractions of Bovine Serum

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Abstract
There is a diversity of carriers of the J blood-group activity of bovine serum. The qualitative and quantitative distribution of the J activity on different carriers was studied, using various fractionation procedures. Approximately one third of J activity was found in the total lipids extracted from serum, two thirds in the lipid-free residue precipitated by lipid extraction. One third of the lipid J substance was found to be bound to the very low density lipoprotein, two thirds to the low density lipoprotein, while the high density lipoprotein was completely free of J activity. All non-lipidic J substance was present in the lipid-free protein. There was no J activity in the low molecular weight mucoproteins of serum and in the apoproteins of the lipoprotein fractions. The lipoprotein fractions were prepared by ultracentrifugation at different solvent densities. The lipoprotein fractions were characterized by chemical analyses and physical properties. The lower total cholesterol concentration of bovine serum, as compared to human serum, is reflected in a lower concentration of low density lipoprotein. The results obtained by ultracentrifugation coincide with the results obtained by precipitation of "beta-lipoproteins" with dextran sulfate and calcium chloride and with results obtained by gel filtration of bovine serum. The "beta-lipoprotein" fraction contains lipoproteins of very low and low density, and probably chylomicrons and a variety of other proteins, however no high density lipoprotein.