A non-essential amino acid. Non-essential means that although we require it to survive and thrive, we do not require it in the diet. We have to get it from somewhere though! Our metabolism achieves this by producing proline from other amino acids. Keep in mind that although we can synthesize proline, we cannot synthesize all amino acids. The amino acids we cannot produce are called essential amino acids. In nature, proline is found in proteins. Proline and the other 19 biologically active amino acids, are the building blocks of proteins, which are essential for our survial.