In-vitro carboxymethylation of low density lipoprotein alters its metabolism via the high-affinity receptor.

Carboxymethylation of lysine residues has been shown to result from oxidation of glycated proteins in vivo and in vitro leading to an augmentation of proteins' net negative charge. The metabolism of carboxymethylated low density lipoprotein (LDL) was studied in cultured human fibroblasts 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 of LDL into mouse peritoneal macrophages via the scavenger receptor, which was stimulated by acetylation, was not affected.