Hydroxylysine (Hyl) is an amino acid with the molecular formula C₆H₁₄N₂O₃. It was first discovered in 1921 by Donald Van Slyke as the 5-hydroxylysine form.^[1] It arises from a post-translational hydroxy modification of lysine. It is most widely known as a component of collagen.^[2]

Hydroxylysine

Names
IUPAC name (5R)-5-Hydroxy-L-lysine
Systematic IUPAC name (2S,5R)-2,6-Diamino-5-hydroxyhexanoic acid
Other names 5-Hydroxy-L-lysine α,ɛ-Diamino-δ-hydroxycaproic acid
Identifiers
CAS Number	1190-94-9 N
3D model (JSmol)	Interactive image
ChemSpider	2297721 Y
ECHA InfoCard	100.013.388
KEGG	C16741 N
MeSH	Hydroxylysine
PubChem CID	3032849
UNII	2GQB349IUB Y
InChI InChI=1S/C6H14N2O3/c7-3-4(9)1-2-5(8)6(10)11/h4-5,9H,1-3,7-8H2,(H,10,11)/t4-,5+/m1/s1 Y Key: YSMODUONRAFBET-UHNVWZDZSA-N Y
SMILES C(C[C@@H](C(=O)O)N)[C@H](CN)O
Properties
Chemical formula	C6H14N2O3
Molar mass	162.189 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

It is biosynthesized from lysine via oxidation by lysyl hydroxylase enzymes. The most common form is the (5R) stereoisomer found in collagen. However, the enzyme JMJD6 has recently been shown to be a lysyl hydroxylase which modifies an RNA splicing factor producing the (5S) stereoisomer. Additionally, in E. coli, there has been at least one lysine N-hydroxylase enzyme identified, named IucD.^[3]