L-Proline

L-Proline is one of the 20 amino acids that are used to synthesize proteins by the human body. L-proline is the only proteinogenic amino acid that is a secondary amine, meaning that its amine nitrogen is bound to two alkyl groups. Virtually all of the proteins in the human body contain L-proline, and the only amino acids that are more abundant are alanine and glutamine. L-proline is especially important in the production of collagen, which is a primary component in skin, cartilage and bone.