Proline is an amino acid, which is a building block for protein. It is classified as a proteinogenic amino acid, although it does not contain the amino group -NH2 but is rather a secondary amine. The body can make proline on its own, but it is also consumed in the diet, with a typical diet containing about 5 grams of proline daily. Proline is biosynthetically derived from the amino acid L-glutamate.

Proline is commonly found in turns, alpha helices, and beta sheets, where it acts as a structural disruptor in the middle of regular secondary structure elements. It is also commonly found as the first residue of an alpha helix and in the edge strands of beta sheets.

Proline is used for skin healing, especially in people who have problems keeping enough proline in the body. It is also used as a stabilizer to help some prescription products last longer. However, there is no good scientific evidence to support any of these uses.

In summary, proline is an amino acid that is used to synthesize proteins and is found in turns, alpha helices, and beta sheets. It is consumed in the diet and can also be made by the body. Proline is used for skin healing and as a stabilizer in some prescription products, but there is no good scientific evidence to support these uses.