Allysine

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  3D model of L-Allysine zwitterion
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  Post-translational modification of Lysine

Allysine

Allysine is a derivative of the amino acid lysine, which plays a crucial role in the cross-linking of collagen and elastin in the extracellular matrix of connective tissues. It is an important intermediate in the biosynthesis of these structural proteins, contributing to the stability and mechanical properties of tissues.

Structure and Formation

Allysine is formed through the oxidative deamination of lysine residues in collagen and elastin. This reaction is catalyzed by the enzyme lysyl oxidase, which converts the _-amino group of lysine into an aldehyde group, resulting in the formation of allysine. The chemical structure of allysine is characterized by the presence of an aldehyde group, which is highly reactive and capable of forming covalent cross-links with other allysine residues or with other amino acids such as hydroxylysine.

Role in Collagen and Elastin Cross-linking

The primary function of allysine is to facilitate the cross-linking of collagen and elastin fibers, which is essential for the structural integrity and function of connective tissues. In collagen, allysine residues can react with each other or with hydroxylysine residues to form stable covalent bonds known as Schiff bases or aldol condensation products. These cross-links enhance the tensile strength and durability of collagen fibers.

In elastin, allysine residues participate in the formation of desmosine and isodesmosine, which are unique cross-linking amino acids that provide elasticity to the elastin network. The presence of these cross-links allows elastin to stretch and recoil, a property that is vital for the function of elastic tissues such as blood vessels, lungs, and skin.

Biological Significance

The cross-linking of collagen and elastin by allysine is crucial for maintaining the structural integrity of tissues and organs. Defects in lysyl oxidase activity or allysine formation can lead to connective tissue disorders, such as Ehlers-Danlos syndrome and Menkes disease, which are characterized by weakened connective tissues and impaired tissue function.

Additionally, the accumulation of advanced glycation end-products (AGEs) involving allysine can contribute to the aging process and the development of age-related diseases, such as atherosclerosis and diabetes mellitus.

Related Pages

• Lysine
• Collagen
• Elastin
• Lysyl oxidase
• Connective tissue