Apolipoprotein C (apoC, English apolipoprotein C, apoC ) - in molecular biology is a family of four low molecular weight apolipoproteins , designated: CI, C-II, C-III and C-IV.
The C apolipoprotein family often acts as the surface components of the VLDL and HDL chylomicrons . In most cases, class C apolipoproteins are mainly associated with HDL (high density lipoproteins). In the process of digestion and absorption of dietary fats, the class C apolipoproteins contained in them are predominantly redistributed to the surface of triglyceride-containing lipoproteins of very low density and VLDL chylomicrons (very low density lipoproteins) [1] .
Structure and isoforms
Four isoforms of apoC are synthesized in the body: CI , C-II , C-III and C-IV .
| Isoform | Structure | Lipoprotein | Function |
|---|---|---|---|
| Apolipoprotein C1 | Consists of 57 amino acids , the molecular weight of the protein is 6.6 kDa. The secondary structure includes an amphiphilic α-helix (the hydrophobic part is associated with the lipid, and the hydrophilic part is exposed to the aqueous medium). | VLDL , HDL chylomicrons . | Lecithin cholesterol acyltransferase activator ( LHAT ). It is able to inhibit cholesterol ester transfer protein (ECB), hepatic lipase and phospholipase 2 . Refers to exchanged apolipoproteins. |
| Apolipoprotein C2 | Consists of 79 amino acids, the molecular weight of the protein is 8.8 kDa. | An activator ( cofactor ) of extrahepatic lipoprotein lipase . Refers to exchanged apolipoproteins. | |
| Apolipoprotein C3 | Consists of 79 amino acids, the molecular weight of the protein is 8.75 kDa. According to the degree of sialylation, 3 isoforms of apoC30, apoC31 and apoC32 protein are distinguished. | Participates in the exchange of triglycerides - it is able to suppress ( inhibit ) lipoprotein lipase (however, this is shown in vitro ) and activate LHAT. Refers to exchanged apolipoproteins. | |
| Apolipoprotein C4 | Consists of 127 amino acids, the molecular weight of the protein is 11 kDa. According to the degree of sialylation, 5 isoforms of apoC4 are distinguished. | VLDL, HDL | The biological role is unknown. |
Notes
- ↑ Mahley RW, Innerarity TL, Rall SC, Weisgraber KH Plasma lipoproteins: apolipoprotein structure and function (rum.) // J. Lipid Res. . - 1984. - Decembrie ( t. 25 , nr. 12 ). - P. 1277-1294 . - PMID 6099394 . (eng.)