What is "hydroxylysine"

n. (context organic compound English) A hydroxy derivative of lysine.

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

It is biosynthesized from lysine via oxidation by lysyl hydroxylase enzymes. The most common form is the (5R) stereoisomer found in collagen. However, 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.