Amino acids have many functions in the body. They are the building blocks for all body proteinsstructural proteins that build muscle, connective tissue including skin, bone and other structures, and functional proteins in the form of thousands of metabolically active enzymes. Amino acids provide the body with the nitrogen that is essential for growth and maintenance of all tissues and structures. Aside from these general functions, individual amino acids also have specific functions in many aspects of human physiology and biochemistry. Amino acids serve as precursors for many nitrogenous substances. These include heme, purines, pyrimidines, hormones, and neuro-transmitters, including biologically active peptides. L-Proline plays an important role in skin health and collagen formation as the body can convert proline into hydroxyproline, which is used by the body to make into collagen.