Allysine is a derivative of

lysine Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. It contains an α-amino group (which is in the protonated form under biological conditions), an α-carboxylic acid group (which is in the deprotonated − ...

, used in the production of

elastin Elastin is a protein that in humans is encoded by the ''ELN'' gene. Elastin is a key component of the extracellular matrix in gnathostomes (jawed vertebrates). It is highly elastic and present in connective tissue allowing many tissues in the bo ...

and

collagen Collagen () is the main structural protein in the extracellular matrix found in the body's various connective tissues. As the main component of connective tissue, it is the most abundant protein in mammals, making up from 25% to 35% of the whol ...

. It is produced by the actions of the enzyme

lysyl oxidase Lysyl oxidase (LOX), also known as protein-lysine 6-oxidase, is an enzyme that, in humans, is encoded by the ''LOX'' gene. It catalyzes the conversion of lysine molecules into highly reactive aldehydes that form cross-links in extracellular ma ...

in the

extracellular matrix In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide s ...

and is essential in the crosslink formation that stabilizes collagen and elastin.

Clinical relevance

Large quantities of

and

present in tissue may lead to

metastasis Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, the ...

: spread of disease. Fibrous tissue containing oxidized collagen may result in a condition known as

fibrosis Fibrosis, also known as fibrotic scarring, is a pathological wound healing in which connective tissue replaces normal parenchymal tissue to the extent that it goes unchecked, leading to considerable tissue remodelling and the formation of perma ...

. The

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or ...

of lysine residues present in collagen creates the aldehyde, aminoadipic-δ-semialdehyde (allysine). Increased allysine concentration in tissues has been correlated to the presence of fibrosis. To qualify protein carbonyls in biological systems, most research studies use the dinitrophenylhydrazine (DNPH) process. The study of particular protein carbonyls, such as allysine, reveals more about specific redox processes and mechanisms at the molecular level. Allysine and its oxidation product, α- amino adipic acid (α-AA), have been discovered to also be diabetes risk indicators. To get a better understanding of this concept, human serum albumin was incubated for 32 hours at 37 degrees Celsius in the presence of FeCl₃ (25 μM) and increasing glucose concentrations. Both allysine and α-AA levels were found to rise as glucose levels increased which lead to the depletion of tryptophan. Regarding the underlying functions of tryptophan and its metabolites, depletion of tryptophan and its metabolites may result in additional physiological problems such as coronary artery disease and neurological complications.

Allysine quantification

Allysine can be reacted with sodium 2-naphthol-6-sulfonate to produce a

fluorescent Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, ...

bis-naphtol allysine product. Allysine can then be quantified through use of

high-performance liquid chromatography High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify each component in a mixture. It relies on pumps to pa ...

(HPLC). This method of detection was used to show that allysine has a 2.5 fold higher concentration in fibrotic vs. normal tissue.

References

Amino acids Aldehydes Aldehydic acids {{Biochemistry-stub

Clinical relevance

Allysine quantification

See also

References