Elastin
| Elastin | ||
|---|---|---|
| Properties of human protein | ||
| Mass / length primary structure | 760 amino acids | |
| Isoforms | 13 | |
| Identifier | ||
| Gene name | ELN | |
| External IDs | ||
| Occurrence | ||
| Parent taxon | Vertebrates | |
Elastin (or its soluble precursor tropoelastin ) is a fiber protein found in vertebrates with the exception of round- mouthed animals . It is one of the structural proteins because its function is responsible for shaping and holding, in particular it ensures that large blood vessels such as the aorta can stretch . Mutations in the ELN - gene can cause hereditary diseases such Dermatochalasis , Williams Syndrome , Cutis Laxa and subvalvular congenital aortic stenosis (SVAS).
The composition of elastin is similar to that of collagen , but it does not contain hydroxylysine , but instead contains a considerable proportion of valine (15.6%). Lysine residues can be oxidized to allysine by the enzyme lysyl oxidase ( EC 1.4.3.13 ) . 3 allysines and a lysine can be converted into a ring-shaped desmosine , which contributes to the elasticity of the entire molecule.
Elastin is a protein network and consists of networked elastin units. Elastin is secreted by the cells in a soluble form and then cross-linked by the enzyme lysyl oxidase (LOX). The amino acid lysine is responsible for this cross-linking. Elastin is an extremely long-lived protein with a half-life of 74 years. The formation of elastin begins before birth and continues in humans in the first years of life. After that, practically no new, functional elastin is formed. Elastin has a high resistance to proteases. Proteases that can cleave elastin are called elastases . This family includes various serine proteases such as pancreatic elastase or cathepsin G, metalloproteases such as MMP-12 and cysteine proteases, e.g. B. Cathepsin K, L or S.
In contrast to collagen, elastin is elastic, more precisely entropy elastic . Elastin is found in the lungs, skin and blood vessels and gives them elasticity and resilience. It can also be used in tissue engineering to create replacement arteries .
structure
Depending on the splice variant, human tropoelastin has a molecular mass between 49 and 69 kDa and consists of the following two types of domains, which are arranged alternately:
- Hydrophobic domains made up of repeat units of the amino acids glycine (G), valine (V), proline (P) and alanine (A). Frequently repeating sequence motifs are e.g. B. VPGVG, GGVP or GVGVAP.
- Hydrophilic domains that are typically rich in lysine (K), proline, and alanine. These domains are required for networking. They consist of areas in which one lysine is separated from the next by two or three alanines (e.g. AAAKAAKAA) or in which lysine lies next to proline (e.g. KPLKP).
Metabolism and synthesis
Soluble elastin is secreted by various cells and immediately after leaving the cell it is cross-linked in the extracellular matrix to form elastin. The crosslinking takes place through the copper-dependent enzyme lysyl oxidase , which oxidizes the ε- amino groups of the lysine, releasing hydrogen peroxide and ammonia . This creates α-amino-adipine-δ-semi aldehyde ( allysine ). This can crosslink with another free amine to form a dehydrolysinonorleucine, whereas allysinaldol is formed when two allysines are condensed . These two products can then condense further to form desmosin .
Since tropoelastin is crosslinked very quickly in vivo, it is only found in extremely low concentrations in the tissue. Tropoelastin was detected by rearing animals in which the production of active lysyl oxidase was inhibited.
Individual evidence
- ↑ InterPro entry
- ↑ UniProt P15502
- ↑ Entry on Desmosine. In: Römpp Online . Georg Thieme Verlag, accessed on March 5, 2011.
- ↑ a b Oliver Türk: Material use of renewable raw materials . 1st edition. Springer Vieweg, Wiesbaden 2014, ISBN 978-3-8348-1763-1 , p. 159 .