The role of processing of the oligosaccharide chains in the affinity of lipoprotein lipase (LPL) for heparin was examined in 3T3-L1 adipocytes. 43% of 35S-labeled LPL subunits in tunicamycin (TUN)-treated cells did not bind to a heparin-Sepharose column and 46% was eluted with 0.6 M NaCl. 11% of LPL subunits in castanospermine (CSTP)-treated cells did not bind to the column and 38% was eluted with 0.6 M NaCl. In contrast, as in untreated cells, LPL subunits in 1-deoxymannojirimycin (dMM)-treated and swainsonine (SW)-treated cells almost all bound to the column and over 93% of the subunits bound were eluted with 1.5 M NaCl. Thus, core glycosylation and subsequent removal of the distal glucose residue from oligosaccharide chains of LPL in the endoplasmic reticulum (ER) is required for acquisition of a higher affinity for heparin.