Exchangeable apolipoproteins are water-soluble protein components of lipoproteins that solubilise lipids and regulate their metabolism by binding to cell receptors or activating specific enzymes. Structural domains comprising this superfamily share the structure of apolipoprotein C-I (ApoC-I), the smallest exchangeable apolipoprotein which transfers among HDL (high density lipoprotein), VLDL (very low-density lipoprotein) and chlylomicrons. ApoC-1 activates lecithin:choline acetyltransferase (LCAT), inhibits cholesteryl ester transfer protein, can inhibit hepatic lipase and phospholipase 2 and can stimulate cell growth. ApoC-1 delays the clearance of beta-VLDL by inhibiting its uptake via the LDL receptor-related pathway PMID:11580293.