Base Information of Peptides

    A peptide is a biologically occurring chemical compound containing two or more amino acids connected to one another by peptide bonds. A peptide bond is a covalent bond that is formed between two amino acids when a carboxyl group or C-terminus of one amino acid reacts with the amino group or N-terminus of another amino acid in a condensation reaction (a molecule of water is released during the reaction). The resulting bond is a CO-NH bond and forms a peptide, or amide molecule. Likewise, peptide bonds are amide bonds.

    Peptides are formed both naturally within the body and synthetically in the laboratory. The body manufactures some peptides organically, such as ribosomal and non-ribosomal peptides. In the laboratory, modern peptide synthesis processes can create a virtually boundless number of peptides using peptide synthesis techniques like liquid phase peptide synthesis or solid phase peptide synthesis. While liquid phase peptide synthesis has some advantages, solid phase peptide synthesis is the standard peptide synthesis process used today. Read more about peptide synthesis.

    Peptides are generally classified according to the amount of amino acids contained within them. The shortest peptide, one composed of just two amino acids, is termed a “dipeptide.” Likewise, a peptide with 3 amino acids is referred to as a “tripeptide.” Oligopeptides refer to shorter peptides made up of relatively small numbers of amino acids, generally less than ten. Polypeptides, conversely, are typically composed of more than at least ten amino acids. Much larger peptides (those composed of more than 40-50 amino acids) are generally referred to as proteins.

Peptides are generally divided into several classes. These classes vary with how the peptides themselves are produced. For example, ribosomal peptides are produced from the translation of mRNA. Ribosomal peptides often function as hormones and signaling molecules in organisms. These can include tachykinin peptides, vasoactive intestinal peptides, opioid peptides, pancreatic peptides, and calcitonin peptides. Antibiotics like microcins are ribosomal peptides produced by certain organisms. Ribosomal peptides often go through the process of proteolysis (the breakdown of proteins into smaller peptides or amino acids) to reach the mature form.