Editing Collagen (section)

===Amino acids===
Collagen has an unusual amino acid composition and sequence:
* Glycine is found at almost every third [[residue (biochemistry)|residue]].
* Proline makes up about 17% of collagen.
* Collagen contains two unusual derivative amino acids not directly inserted during [[translation (genetics)|translation]]. These amino acids are found at specific locations relative to glycine and are modified post-translationally by different enzymes, both of which require vitamin C as a cofactor.
** [[Hydroxyproline]] derived from proline
** [[Hydroxylysine]] derived from lysine – depending on the type of collagen, varying numbers of hydroxylysines are [[glycosylation|glycosylated]] (mostly having [[disaccharide]]s attached).

[[Cortisol]] stimulates [[Amide hydrolysis|degradation]] of (skin) collagen into amino acids.<ref>{{cite journal | vauthors = Houck JC, Sharma VK, Patel YM, Gladner JA | title = Induction of collagenolytic and proteolytic activities by anti-inflammatory drugs in the skin and fibroblast | journal = Biochemical Pharmacology | volume = 17 | issue = 10 | pages = 2081–2090 | date = October 1968 | pmid = 4301453 | doi = 10.1016/0006-2952(68)90182-2 }}</ref>