11. Uncatalysed, the hydrolysis of peptide bonds is extremely slow, taking hundreds of years. 12. Proteins are polymer chains made of amino acids linked together by peptide bonds . 13. An example is glycylglycine, consisting of two glycine molecules joined by a peptide bond . 14. The phosphoric acid would act as a catalyst for the formation of peptide bonds . 15. However, not all peptide bonds are formed in this way. 16. These DNP-amino acids are moderately stable under acid hydrolysis conditions that break peptide bonds . 17. This condensation reaction yields the newly formed peptide bond and a molecule of water. 18. The amino acid residues are always joined by peptide bonds . 19. Note that water is required for normal peptide bond cleavage of the iminolactone intermediate. 20. Similar methods may be used to specifically cleave tryptophanyl, aspartyl, cysteinyl, and asparaginyl peptide bonds .
