Peptide Topics

• polypeptides proteins
• aerobic organisms
• peptide bond
• biological compounds
• amide bond
• amyloid beta peptide
• synthetic techniques
• antioxidant defenses
• amino acid residue
• amino acids
• hydroxylation
• glycosylation
• propeptides
• peptides
• proteolysis
• ligation
• glutathione
• bloodstream
• caveats
• nuances

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Peptide, Peptide

The link between one amino acid residue and the next is known as an amide bond or a peptide bond.

The distinction is that peptides are short and polypeptides/proteins are long. There are several different conventions to determine these, all of which have caveats and nuances.

However, with the advent of better synthetic techniques, peptides as long as hundreds of amino acids can be made, including full proteins like ubiquitin. Native chemical ligation has given access to even longer proteins, so this convention seems to be outdated.

Long peptides, such as the amyloid beta peptide linked to Alzheimer's disease, can be considered proteins; and small proteins, such as insulin, can be considered peptides.

They are often subjected to proteolysis to generate the mature form. These function, typically in higher organisms, as hormones and signaling molecules. Some organisms produce peptides as antibiotics, such as microcins.

However, these peptides frequently have posttranslational modifications, such as phosphorylation, hydroxylation, sulfonation, palmitylation, glycosylation and disulfide formation. In general, they are linear, although lariat structures have been observed.

The most common non-ribosomal peptide is glutathione, which is a component of the antioxidant defenses of most aerobic organisms.

In addition to containing small peptides, the resulting spray-dried material includes fats, metals, salts, vitamins and many other biological compounds.

In this case the peptides are most often generated by in-gel digestion after electrophoretic separation of the proteins.

All of these peptides are synthesized by cells as longer "propeptides" or "proproteins" and truncated prior to exiting the cell. They are released into the bloodstream where they perform their signalling functions.

Source: Wikipedia > Peptide