Hydroxylysine is an amino acid related to collagen.
What is collagen?
Collagen is the most abundant protein in your body. It is the major component of connective tissues that make up several body parts, including tendons, ligaments, skin and muscles.
What is lysine?
Lysine is one of nine essential amino acids in humans required for growth and tissue repair. A portion of the lysine of collagen is modified to hydroxylysine, which provides a marker for bone loss due to the turnover of collagen during bone resorption.
What is hydroxyproline?
Collagen metabolism releases a variety of collagen constituents into the circulation. These include amino- and carboxy-terminal extension peptides, pyridinoline, and deoxypyridinoline cross-links, and hydroxyproline.
Hydroxyproline in plasma appears as both peptide bound and free forms. Bone resorption is the major contributor to collagen turnover, and the constituent molecules, including hydroxyproline, are useful as markers of the rate of bone matrix resorption. Hydroxyproline is most useful in conditions associated with markedly increased bone resorption (Paget’s disease, malignancy, hyperparathyroidism).
Both hydroxylysine and hydroxyproline are indicators of liver disease. However, hydroxylysine has the strongest correlation, possibly because dietary intake of collagen can influence hydroxyproline levels.
Changes in hydroxylysine excretion with cadmium loading in experimental animals indicate that cadmium interferes with collagen synthesis.
References:
http://clinchem.aaccjnls.org/content/45/5/676
http://www.hmdb.ca/metabolites/HMDB0000450
Hydroxylysine
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