Hydroxyproline

**Semantic type:** Amino Acid, Peptide, or Protein

**Definition:** A nonessential amino acid derivative formed during post-translational protein modification through hydroxylation of the amino acid proline by the enzyme prolyl hydroxylase which requires vitamin C as a co-factor. Hydroxyproline is a major component of the protein collagen and plays a key role in the stability of the collagen triple helix. It can be used as an indicator to determine the amount of collagen. Increased hydroxyproline levels in the urine and/or serum are normally associated with degradation of connective tissue. Vitamin C deficiency decreases the conversion of proline to hydroxyproline, which leads to reduced collagen stability.

**Synonyms:** - 4-Hydroxy-L-proline - HYDROXYPROLINE