INVITRO CARBOXYMETHYLATION OF LOW-DENSITY-LIPOPROTEIN ALTERS ITS METABOLISM VIA THE HIGH-AFFINITY RECEPTOR

Carboxymethylation of lysine residues has been shown to result from ox idation of glycated proteins in vivo and in vitro leading to an augmen tation of proteins' net negative charge. The metabolism of carboxymeth ylated low density lipoprotein (LDL) was studied in cultured human fib roblasts and mouse peritoneal macrophages. In vitro carboxymethylation was achieved by incubation of LDL with glyoxylic acid in the presence of Na(CN)BH3. Carboxymethylation inhibited metabolism of LDL via the high affinity receptor in fibroblasts as did methylation. The uptake o f LDL into mouse peritoneal macrophages via the scavenger receptor, wh ich was stimulated by acetylation, was not affected.