Proline and its derivatives are often used as asymmetric catalysts in proline organocatalysis reactions. These six are arginine, cysteine, glycine, glutamine, proline and tyrosine. These six are arginine, cysteine, glycine, glutamine, proline, and tyrosine. Proline and arginine are derived from glutamate. Gelatin has proline, hydroxyproline and glycine in its polypeptide chain. The pathways linking arginine, glutamine, and proline are bidirectional. Profilin also binds sequences rich in the amino acid proline in diverse proteins. Domoic acid is a structural analog of kainic acid, proline, and endogenous excitatory neurotransmitter glutamate. This family includes&colon; glutamate, glutamine, proline, and arginine. It also affects the rate of peptide bond formation between proline and other amino acids. The amino acids proline and hydroxyproline are, in a structural sense, derivatives of pyrrolidine. This modification of the proline residue increases the stability of the collagen triple helix. Casein contains a high number of proline residues, which do not interact. Tannin-binding capacity of salivary mucin is directly related to its proline content. The CBS reduction and proline catalysed aldol condensation are prominent examples.