Proline is a nonessential amino that is found in all mammalian tissue. It exists as the main component of protein collagen, accounting for some 20% of this fibrous compound. [1] Proline assists in the binding and support of all connective tissue structures located throughout the body. Proline was first isolated from casein in 1901. Soon after, scientists discovered that proline is the only amino readily soluble in alcohol. This characteristic makes proline unique among all amino acids.

Synthesis of glutamic acid may provide the body with ample amounts of proline. Other amino acids partially responsible for the formation of proline include both glutamine and ornithine. Because proline exists in a nonessential classification, it does not require dietary sources for processing.