ChEBI: Cis-4-hydroxy-L-proline is l-Proline in which a hydrogen at the 4-position of the pyrrolidine ring is substituted by a hydroxy group (S-configuration). It has a role as a metabolite. It is a non-proteinogenic L-alpha-amino acid and a 4-hydroxyproline. It is a tautomer of a cis-4-hydroxy-L-proline zwitterion.