Apolipoprotein B (Apo B)

1. Apolipoprotein B (apoB) is the main apolipoprotein of chylomicrons (CM), very low density lipoproteins (VLDL), and low density lipoproteins (LDL). 
2. ApoB occurs in the plasma in 2 main forms, apoB48 and apoB100, which are bound to lipoproteins. 
3. ApoB48 is synthesized exclusively by the gut. [ApoB48 = Gut origin]
4. ApoB100 is synthesized by the liver. [ApoB100 = Liver origin]
5. ApoB100 is larger than apoB48.    [100 > 48]
6. ApoB is not water-soluble (ie, it is hydrophobic and bound to lipids in lipoproteins).
7. ApoB does not leave the lipoprotein (ie, it not exist as a free entity in plasma).
8. ApoB mediates uptake of B-containing lipoproteins (CM Rm, VLDL remnants, IDL and LDL).
9. ApoB100 is necessary for hepatic LDL uptake.
10. ApoB48 is necessary for CM Rm uptake.

More at http://omim.org/entry/107730