Proline

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

**Definition:** A cyclic, nonessential amino acid (actually, an imino acid) in humans (synthesized from glutamic acid and other amino acids), Proline is a constituent of many proteins. Found in high concentrations in collagen, proline constitutes almost a third of the residues. Collagen is the main supportive protein of skin, tendons, bones, and connective tissue and promotes their health and healing. (NCI04)

**Synonyms:** - (S)-Pyrrolidine-2-carboxylic acid - PROLINE - Pro