Low density lipoprotein biochemistry
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Cafer Zorkun, M.D., Ph.D. [2]; Rim Halaby, M.D. [3]
Overview
Low-density lipoprotein (LDL) belongs to the lipoprotein particle family. Its size is approx. 22 nm but since LDL particles contain a changing number of fatty acids they actually have a mass and size distribution. Each native LDL particle contains a single apolipoprotein B-100 molecule (Apo B-100, a protein with 4536 amino acid residues) that circles the fatty acids keeping them soluble in the aqueous environment.[1] There is a direct association between cardiovascular death and duration of elevated plasma LDL-cholesterol (LDL-C) levels. In most cases, elevated LDL is a contribution of both polygenic factors and environmental influences.[2]
Biochemistry
Structure
| Lipoprotein | Density | Size | % Protein | % Cholesterol | % Triglyceride | Major Lipid | Apolipoprotein |
| HDL |
For more information about the biochemistry of all lipoproteins, click here.
- Low-density lipoprotein (LDL) belongs to the lipoprotein particle family. It has a discoid shape with an average diameter of approximately 20 nm.[3] However, LDL is considered a heterogeneous molecule due to fluctuating density, size, and flotation rate.
- The average composition of LDL is 20% protein, 20% phospholipids, 40% cholesteryl esters, 10% unesterified cholesterol, and 5% triglycerides.[4]
- The LDL particle can be structurally divided into 3 layers according to molecular orientational behavior:
- Outer surface layer with tangential orientation: It forms a shell composed of phospholipid monolayer to cover the core. The phospholipid monolayer is organized in a way that hydrophilic residues with polar head groups interact with the outer aqueous solvent; while the inner hydrophobic residues face the lipid interior.
- Interfacial layer with radial orientation
- Apolar lipid core with random orientation: It contains cholesteryl esters and triglycerides.[4][5]
- Each native LDL particle contains a single apolipoprotein B-100 (Apo-100) molecule. Apo B-100 is a protein with 4536 amino acid residues. It encircles the fatty acids keeping them soluble in the aqueous environment.[3]
- ApoB-100 covers the surface layer of LDL in a heterogeneous fashion, covering one hemisphere of LDL, while keeping other surfaces uncovered with exposed lipids.[4]
LDL Receptors
Enzymes Associated with LDL
References
- ↑ Segrest, J. P.; et al. (September 2001). "Structure of apolipoprotein B-100 in low density lipoproteins". Journal of Lipid Research. 42: 1346–1367.
- ↑ Rader DJ, Cohen J, Hobbs HH (2003). "Monogenic hypercholesterolemia: new insights in pathogenesis and treatment". J Clin Invest. 111 (12): 1795–803. doi:10.1172/JCI18925. PMC 161432. PMID 12813012.
- ↑ 3.0 3.1 Segrest JP, Jones MK, De Loof H, Dashti N (2001). "Structure of apolipoprotein B-100 in low density lipoproteins". J Lipid Res. 42 (9): 1346–67. PMID 11518754.
- ↑ 4.0 4.1 4.2 Hevonoja T, Pentikäinen MO, Hyvönen MT, Kovanen PT, Ala-Korpela M (2000). "Structure of low density lipoprotein (LDL) particles: basis for understanding molecular changes in modified LDL". Biochim Biophys Acta. 1488 (3): 189–210. PMID 11082530.
- ↑ Prassl R (2011). "Human low density lipoprotein: the mystery of core lipid packing". J Lipid Res. 52 (2): 187–8. doi:10.1194/jlr.E013417. PMC 3023539. PMID 21131533.