Proline is an amino acid found in proteins and enzymes. It is unique among other amino acids because its side chain is attached to the nitrogen atom of the backbone, which causes it to form a ring in the middle of the molecule and cascade in a cyclic structure. It is hydrophobic, nonpolar, and generally unreactive. Proline is essential for maintaining the health of collagen and elastin, and it is involved in many other biological activities, including growth, repair, and metabolism. Proline is commonly found in higher concentrations in the muscles and brains of humans, as well as other mammals. In the body, Proline helps provide stability to molecular structures, prevents enzymes from denaturing, and is an important fuel source in cells and tissues.