Proline

Between 1899 and 1906, Hermann Emil Fischer discovered the amino acid Proline. Proline, abbreviated as Pro or P, is one of the twenty DNA-encoded amino acids. The systematic name for Proline is Pyrrolidine-2-carboxylic acid. It is not considered an essential amino acid; therefore the human body can synthesize it. Proline is the only cyclic amino acid and is biosynthetically derived from the amino acid,  L-glutamate and its immediate precursor is the imino acid (S)-1-pyrroline-5-carboxylate (P5C).¹ An imino acid is any molecule that contains both imino (>C=NH) and carboxyl (-C(=O)-OH) functional groups.² Proline is used a systemmatic catalyst in organic reactions. L-Proline is an osmoprotectant and therefore is used in many pharmaceutical, biotechnological applications.¹ Proline is thermophilic and can withstand an environment with extreme osmotic stress, thus why proline is widely used in pharmaceuticals. In studying Immunology, proline plays a significant role. Proline-rich polypeptides (PRP), such as the proline-rich polypeptide in ovine colostrum has an effect on skin permeability and immune response.³

When researching this amino acid, I found it interesting that, “proline is the only amino acid that does not form a blue/purple colour when developed by spraying with ninhydrin for uses in chromatography. Proline, instead, produces an orange/yellow colour.”¹ In our Organic I and II labortories, we use chromatography. The pK value for the amide is 11.0 and the pK value for the carboxyl group is 2.0.⁴

1. http://en.wikipedia.org/wiki/Proline

2. http://en.wikipedia.org/wiki/Osmoprotectant

3.  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1457668/
4. http://www.biology.arizona.edu/biochemistry/problem_sets/aa/proline.html