L-Proline-d₃is intended for use as an internal standard for the quantification of L-proline by GC- or LC-MS. L-Proline is a nonessential amino acid.¹It contains a pyrrolidine ring, which contains the α-amino nitrogen, and is highly rigid, properties that affect protein conformation and folding and can cause kinks and turns in protein secondary structure.^1,2It is a substrate for the proton-coupled amino acid transporter 1 (PAT1) and an inhibitor of acetylcholinesterase (AChE; K_i= 86 µM).^3,4L-Proline accumulates in plants under environmental stress and is important for environmental stress tolerance through its involvement in protein synthesis, redox balance maintenance, osmoprotection, and signaling.⁵

1.Lodish, H., Berk, A., Zipursky, L., et al.Hierarchical structure of proteinsMolecular cell biology(2000) 2.MacArthur, M.W., and Thornton, J.M.Influence of proline residues on protein conformationJ. Mol. Biol.218(2)397-412(1991) 3.Thondorf, I., Voigt, V., SchÄfer, S., et al.Three-dimensional quantitative structure-activity relationship analyses of substrates of the human proton-coupled amino acid transporter 1 (hPAT1)Bioorg. Med. Chem.19(21)6409-6418(2011) 4.VÉgner, L., Peragovics, Á., Tombor, L., et al.Experimental confirmation of new drug-target interactions predicted by drug profile matchingJ. Med. Chem.56(21)8377-8388(2013) 5.Szabados, L., and SavourÉ, A.Proline: A multifunctional amino acidTrends Plant Sci.15(2)89-97(2010)