What are Peptides?
ď śPeptides are short chains of amino acids monomer that are linked by amide bonds. Amide bonds are also known as peptide bond and both are used interchangeably to denote one another. ď śOne molecule of water is eliminated from the condensation of amino acids to form peptide. The result is peptide or amine bonds.
ď ś Either end of dipeptide can react to give rise to tripeptide. The tripeptide in turn can condense with another amino acid and so on. ď śThis keeps giving rise to formations of long chains of amino acids. For instance, insulin, which is a common protein, has 51 amino acids units in two linked chains.
ď ś Peptides are so numerous because of their ability to be synthesized into very long chains. Peptides and proteins are similar in structure but there are noticeable differences between them. A protein is polymer of amino acids. It is a poly peptide containing several amino acids linked together.
ď śTypes of Peptides ď śThe shortest peptides known are dipeptides. It consists of two amino acids linked together by a single peptide bond with the loss of water molecule. The biosynthesis of peptide bonds always requires an input of free energy. Peptides bonds are quite stable kinetically. The lifetime of a peptide bond in an aqueous solution in the absence a catalyst is close to a thousand years.
ď śTripeptide is another type of peptides. Glutathione is one the most important and well known tripeptide. It is commonly found in significant concentrations in all tissues. It contains glutamic acid, cysteine, and glycine. Instead of the usual backbone that is characteristics of peptides, the carboxyl acid side chain is part of the backbone peptide structure. The normal carboxyl group is the so called side chain in this case.
ď śPolypeptide chain consists of a regularly repeating part. This is the main chain. It can also be referred to as the backbone of the polypeptides. It is very rich in hydrogen bonding potential. Apart from the backbone, there is also the variable part. This is made up of distinctive side chains.
ď śEach residue of a polypeptide chain consists of carbonyl group. The carbonyl group is good hydrogen-bond acceptor with the exception of Proline which is an excellent donor of hydrogen bond. These two groups highly interact with each other. They also interact with the functional groups present on the side chains. This interaction is of great importance in stabilizing the polypeptide chains
ď śMost natural polypeptide chains are made up of 50 and 2000 amino acid residues. They are commonly known as proteins. When the chains are small, it is called Oligopeptides or simply peptides. ď śExamination of the geometry of polypeptides reveals a number of outstanding characteristics. These include the following:
Peptides bond are mainly planar. They have considerable double bond character. This prevent rotation about this bond Inability of the bonds to rotate account for planarity Trans and cis configuration is possible for a peptide bond. However, the most commonly observed is trans configuration.
Classes of Peptides Depending on how they are produced, Peptides are usually divided into several classes. The classes of Peptides are as follows: Milk peptides Ribosomal peptides Nonribosomal peptides
ď śDifference between Peptides and Proteins ď śPeptides can be distinguished from proteins on the basis of size. A peptide is generally believed to have less than 70 amino acids. Proteins usually consist of one or more polypeptides and this gives rise to long chains. Protein can simply be defined as a polymer of amino acids.
ď śWhen amino acids are incorporated into peptides, they are called residues. This is due to the release of either a hydrogen ion from the amine end or a hydroxyl ion from the carboxyl end. At times, both may occur as there is release of water molecules during the formation of each amide bond.
There are so many things to know about peptides. The subsequent articles will address uses, advantages, importance and benefits of peptides to human life. Find where to buy peptides: