A COMPARATIVE-STUDY OF LOW-DENSITY-LIPOPROTEIN INTERACTION WITH GLYCOSAMINOGLYCANS

The association between low-density lipoprotein (LDL) and a series of well characterized dermatan and chondroitin sulfates has been investig ated by means of the fluorescence anisotropy technique with competitio n experiments using a fluorescein-labeled high LDL-affinity heparin fr action as a reference. Preparations of glycosaminoglycan (GAG) with su lfation degrees varying over a wide range, as obtained by fractionatio n or by chemical modification, were chosen for this study. The influen ce of chain length, which had been found sizeable in a former study of heparin affinity for LDL, was taken into account with an empirical co rrection of dissociation constants. After this correction, a linear re lationship was found between the logarithm of dissociation constants a nd the number of sulfate groups per disaccharide unit, n(s), both for dermatan and chondroitin sulfates, and for heparins. At comparable n(s ) values, however, dermatan sulfates and heparins, which contain L-idu ronic acid in their backbone, show higher LDL-affinity than chondroiti n sulfates, which contain only D-glucuronic acid. Though confirming a non-specific, predominantly electrostatic interaction between GAGs and LDL, these results indicate modulation of LDL affinity by the polysac charide backbone.