low density lipoprotein (LDL, beta-lipoprotein)

^[1]^[2]^[3]

Function

LDL is the major cholesterol-carrying protein in plasma.
LDL is catablized via apo B100 - LDL receptor binding & internalization, particularly in liver & steroidogenic cells in adrenal cortex, ovaries, testes, where LDL provides the major source of substrate for synthesis of steroid hormones
SORLA binds LDL & transports it into cells by endocytosis^[3]
in addition to catabolism via the high-affinity LDL receptor pathway, LDL is catabolized by non-specific pathways not subject to feedback regulation
one of these pathways is via the macrophage scavenger receptor which binds & internalizes oxidized forms of LDL
it has been estimated that 35-64% of LDL is degraded by the high-affinity LDL receptor pathway; the remaining is removed by the scavenger cell system
LDL cholesterol levels needed to saturate systemic receptors are about 35 mg/dL

low levels of LDL occur, along with low levels of albumin, prealbumin, & transferrin, in inflammation & malignancy
high levels of LDL may predispose to cardiovascular disease

↑ Primary Hyperlipoproteinemias, Steiner & Shafrir (eds), McGraw Hill, NY, 1991, pg 27
↑ Tietz Textbook of Clinical Chemistry, 2nd ed. Burtis CA & Ashwood ER (eds), WB Saunders Co, Philadelphia PA, 1993, pg 1027
↑ ^3.0 ^3.1 UniProt http://www.uniprot.org/uniprot/Q92673.html