NCIt definition : A hydroxylated amino acid derivative of lysine that arises from post-translational
modification. Lysine is converted into 5-hydroxylysine by lysyl hydroxylase, an oxoenzyme
that catalyzes the hydroxylation of carbon-5 in lysyl residues found in proteins or
peptides. Hydroxylysine residues are required for the formation and stability of triple
helical collagen fibrils.;