Proline

Proline (abbreviated as Pro or P), with the chemical formula C5H9NO2 and a molecular weight of 115.13, is a cyclic imino acid. As an α-imino acid, it is neutral with an isoelectric point of 6.30, and its solubility in water is greater than that of any other amino acid—approximately 162g per 100g of water at 25°C. It is hygroscopic and difficult to crystallize, with a sweet taste. When heated with ninhydrin solution, it produces a yellow compound. Once incorporated into a peptide chain, it can undergo hydroxylation to form 4-hydroxyproline, an important component of animal collagen. Hydroxyproline is also found in various plant proteins, particularly in relation to cell wall formation. Under stress conditions such as drought, high temperature, low temperature, and salinity, plants often exhibit significant accumulation of proline. It has wide applications in clinical settings, biomaterials, industry, and more^[1].