What is a Peptide?
A peptide is a chain of amino acids linked to one another by amide (peptide) bonds. A peptide bond is the covalent chemical bond formed when the carboxyl group of one amino acid reacts with the amino group of another. The word peptide is derived from the Greek word πεσσειν, which means “to digest.” Peptides are an essential part of nature and there are thousands of them that occur naturally in the human body and in animals, but new synthetic peptides are being discovered daily, which show a promising future for health and drug development. The benefits of peptides on health have been demonstrated in numerous research studies related to neurological function, anti-aging, muscle growth, skin wrinkles, growth hormone deficiency, and so forth.
How are peptides made?
Peptides are made both naturally (within the body) and synthetically (via peptide synthesis). Ribosomal peptides and non-ribosomal peptides are manufactured inside the organism. Synthetic peptides are made via liquid-phase peptide synthesis or solid-phase peptide synthesis techniques to ensure maximum requested purity. Numerous peptide suppliers offer custom peptide synthesis of numerous sequence lengths and modifications.
What is the difference between a peptide and a protein?
Peptides are commonly distinguished from proteins based on size, with a general rule of thumb being that a peptide is 50 amino acids in length or less. A polypeptide is a long, unbranched, and continuous strand of amino acids forming a peptide chain. Proteins consist of one or more polypeptides arranged in a biologically functional way. Proteins are quite often bound to ligands, another protein, other macromolecule (DNA, RNA, etc.), or to complex macromolecular assemblies. Many proteins, such as insulin or thymosin beta-4 for example, are commonly referred to as peptides, but they are proteins by definition.
Number of Amino Acids in a peptide?
The shortest peptide length is two amino acids and is known as a dipeptide. A peptide of three amino acids is a tripeptide, a peptide of four amino acids is a tetrapeptide, etc. An undecapeptide has eleven amino acids, a dodecapeptide has twelve amino acids, a tridecapeptide has thirteen amino acids, etc. An icosapeptide has twenty amino acids, a tricontapeptide has thirty amino acids, a tetracontapeptide has forty amino acids, etc.
Different Types of Peptides
Ribosomal peptides
Ribosomal peptides are synthesized by the translation of mRNA and are often subject to proteolysis to generate the mature form. These function, typically in higher organisms, as hormones and signaling molecules (antibiotics, such as microcins). Due to translational restrictions, the amino acid residues involved are only those used by the ribosome. These peptides frequently have post-translational modifications, such as glycosylation or disulfide formation. They are typically linear, although more exotic manipulations do occur, such as racemization of L-amino acids to D-amino acids.
Nonribosomal peptides
These peptides are assembled by peptide-specific enzymes, not by the ribosome. Nonribosomal peptides are frequently cyclic and can have highly complex cyclic structures, although linear nonribosomal peptides are also common. Since the system is related to the machinery for building fatty acids and polyketides, hybrid compounds are often found, while the presence of oxazoles or thiazoles may indicate that the compound was synthesized in this way.
Milk peptides
Milk peptides are formed from milk proteins by enzymatic breakdown by digestive enzymes or by the proteinases formed by lactobacilli during the fermentation of milk.
Peptones
These peptides are derived from animal milk or meat digested by proteolytic digestion.
Peptide fragments
These peptides are fragments of proteins that are used to calculate data related to the source protein. Peptide fragments are commonly the products of enzymatic degradation performed in the laboratory on a controlled sample, but can also be degraded by natural effects. Such an example is AOD9604, more commonly referred to as Human Growth Hormone (hGH) Fragment 177-191 or IGF-1 DES.