Peptide

From ArticleWorld

A peptide is a short molecule that is composed of amino acids linked by peptide bonds also called amide bonds. They are similar to proteins with the exception being that they are much shorter.

Peptides vs. proteins

There are many conventions to determine proteins as opposed to peptides. One such convention is that peptides chains are those that can be made synthetically from amino acids. With new technology however peptide chains as long as hundreds of amino acids can now be made and this includes proteins as well. Another method of distinction used is the use of a cut of point. This is to say that chains up to 50 amino acids in length are considered peptides. This is also disputed as there are claims that this value should be lower. There are some proteins like insulin that are close to the upper limit for peptides. This confusion has led to demands for a clearer definition. One definition that is now used is that peptides are amino acid chains that have not obtained the secondary structure. Thus if they obtain the secondary structure they are considered proteins. There are molecules that are peptides only as they cannot go to the secondary structure but there exist others that can go to this level dependent on environmental conditions.

Classes of peptides

There are three major classes of peptides determined based on there method of production. These are as follows:

• Ribosomal peptides – These are synthesized by mRNA translation and can function as hormones.
• Non-ribosomal peptides – These are synthesized by a modular enzyme complex and are found mainly in plants, fungi and unicellular organisms.
• Digested peptides – These are the result of the breakdown of food. Some foods which breakdown into peptides are: egg, gluten and spinach proteins.