CARBOHYDRATE CONTENT OF APOLIPOPROTEIN-E FROM HUMAN VERY LOW-DENSITY LIPOPROTEINS

The carbohydrate content of the E protein of human very low density lipoprotein (VLDL) was evaluated both by colorimetric methods and by gas liquid chromatography of the trifluoroacetylated 0-methyl glycosides. The major unmodified hexose was noted to be galactose with a mole ratio with respect to protein which ranged from 0.81 to 1.54. N-acetyl glucosamine (molar ratios from 0.52 to 1.76) and N-acetyl galactosamine (molar ratios from 0.73 to 1.59) and the respective unacetylated amino sugars were noted for all of the apoproteins evaluated. Sialic acid (molar ratios from 0.79 to 1.69) was a prominent carbohydrate for each of the E protein preparations. When the apoprotein was exposed to neuraminidase with a resultant loss of two-thirds of the sialic acid, the isoelectric focus behavior was found to be unchanged. The E protein isolated from the very low density lipoproteins of Type III patients (dysbetalipoproteinemia) revealed a carbohydrate content similar to the normals or Type IV patients. © 1979.