Hydroxylysine

• (2S, 5R ) -2,6- diamino-5- hydroxyhexanoic acid

• 28902-93-4
• 13204-98-3 (hydrochloride)

Beige powder (hydrochloride)

Fixed

225-230 ° C ( hydrochloride)

Template: Infobox chemical / molecular formula search available

Hydroxylysine (specifically 5-hydroxy -L-lysine, abbr Hyl ) is a proteinogenic but non-canonical amino acid.

It was discovered by Donald Van Slyke.

Biosynthesis

Although occurring in proteins, this amino acid can not be directly incorporated into polypeptides during translation. Only after incorporation of lysine whose oxidation can be carried out by the enzyme lysyl hydroxylase to hydroxylysine ( post-translational modification ).

Occurrence

5 - hydroxylysine occurs (only in animals and humans ) and in some other glycoproteins such as adiponectin in collagen.

Hydroxylysine was also detected in bacteria, such as in Staphylococcus aureus.

Within a collagen polypeptide, the distribution pattern of the hydroxylated lysines is neither rigid nor completely flexible, that is, in certain positions will never be a hydroxylation found, in some always (except in certain connective tissue diseases ) and other very often to very rare. Within the collagen triple helix hydroxylated lysine occurs almost only in Y position of the Gly- XY sequence, ie: Gly -X - Hyl ( for a more detailed explanation of the Tripelhelixsequenz see collagen). Within the short triple-helical regions of the collagen not it can be found at other locations ( eg, X - HYL -Ala or X - HYL - Ser).

Properties

Functions

5 - hydroxylysine is used in some glycosylations as a starting point for each of the first sugar residue. In collagen, it also fulfilled a this function at other points it serves as a starting point for covalent cross-links between collagen molecules and between all collagen fibrils.

A lack of hydroxylysine in the collagen molecules causes a weakness of connective tissue and is usually attributed to inactive lysyl hydroxylase. Reason for this may be a genetic anomaly ( Ehlers -Danlos syndrome VI) or poisoning (such as the specific inhibitor BAPN = β -aminopropionitrile, accompanying poisoning in lathyrism ). A complete Hydroxylysinmangel is lethal in mammals is then probably not even a live birth possible.

A lack of hydroxylysine within proteins can be compensated directly by absorption of hydroxylysine, since at least one direct incorporation into polypeptides during translation is not physiologically possible. Hydroxylysine, however, offered as a valuable food supplement. A special benefit is questionable.

The prevention of oxidation of lysine to hydroxylysine by the inhibitor BAPN for therapeutic purposes is being considered.

Determination

The hydroxylysine in urine will be taken to quantify the collagen metabolism of bone.