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Hydroxyproline is found in few proteins other than collagen. For this reason, hydroxyproline content has been used as an indicator to determine collagen and/or gelatin amount. However, the mammalian proteins elastin and argonaute 2 have collagen-like domains in which hydroxyproline is formed.
Adams E; Goldstone A (1960). "Hydroxyproline metabolism. III. Enzymatic synthesis of hydroxyproline from Delta1-pyrroline-3-hydroxy-5-carboxylate".
Proline (symbol Pro or P) [4] is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group-NH 2 but is rather a secondary amine.
In nature, proline, hydroxyproline, pipecolic acid and sarcosine are well-known secondary amino acids. Proline is the only proteinogenic secondary amino acids. Other secondary amino acids are non-proteinogenic amino acids. In protein, hydroxyproline is incorporated into protein by hydroxylation of proline.
Procollagen-proline dioxygenase catalyzes the following reaction: L-proline + alpha-ketoglutaric acid + O 2 → (2S, 4R)-4-hydroxyproline + succinate + CO 2. The mechanism for the reaction is similar to that of other dioxygenases, and occurs in two distinct stages: [3] In the first, a highly reactive Fe(IV)=O species is produced.
In 2001, biologically active hydroxyproline-rich glycopeptides were isolated from tobacco which activated the production of protease inhibitors in a similar way to systemin in tomatoes. [1] Although they are structurally unrelated to systemins, their similar function resulted in them being named hydroxyproline-rich systemins (HypSys).
Cleavage of the proline- and hydroxyproline-rich proteins of the Chlamydomonas cell wall; also cleaves azocasein, gelatin and Leu-Trp-Met-Arg-Phe-Ala. This glycoprotein is present in Chlamydomonas reinhardtii gametes. Gram-positive bacteria regulate autolysins with teichoic acid molecules attached to the tetrapeptide of the peptidoglycan matrix.
Two tyrosines separated by a single amino acid, typically valine or another tyrosine, form a short intra-molecular diphenylether crosslink. [11] This can be crosslinked further by the enzyme extensin peroxidase [12] [13] [14] to form an inter-molecular bridge between extensin molecules and thus form networks and sheets.