Peptides - diverse molecules of life
Peptides exist in all organisms, wherever there are cells. The range of their physiological functions is huge. Biologically active peptides can act as hormones, neurotransmitters, growth factors as well as toxins and antibiotics. This is what makes them highly interesting drug leads. They are used for the treatment of autoimmune diseases, cancer and other diseases. Despite some drawbacks, peptides are gaining in importance as candidates for drugs and fuelling interest in research into natural and synthetic peptides.
Peptides consist of amino acids, but are smaller than proteins. Some researchers classify peptides over 50 amino acids long as proteins, whereas others set a benchmark at 100 amino acids. The individual building blocks are joined by relatively rigid peptide bonds, forming a chain of amino acids. These bonds are formed when the carboxyl group (COO-) of one amino acid reacts with the amino (NH3+) group of another, thus releasing a water molecule. In addition to peptide bonds, disulphide bonds can exist within and between peptide chains, as can ester and thioester bonds. Tanja Weil from the University of Ulm reports that most peptides are linear chains of amino acids, but that there are also cyclic and branched peptides.