Peptidomimetic

A peptidomimetic is a small protein-like chain designed to mimic a peptide. They typically arise either from modification of an existing peptide, or by designing similar systems that mimic peptides, such as peptoids and β-peptides. Irrespective of the approach, the altered chemical structure is designed to advantageously adjust the molecular properties such as, stability or biological activity. This can have a role in the development of drug-like compounds from existing peptides. These modifications involve changes to the peptide that will not occur naturally (such as altered backbones and the incorporation of nonnatural amino acids).

A D-peptide is a small sequence of D-amino acids. Since ribosomes are specific to L-amino acids, D-peptides rarely occur naturally in organisms and are not easily digested or degraded. D-peptide peptidomimetics are D-peptides designed to mimic natural L-peptides that commonly have therapeutic properties.

When placed in a nonchiral solvent like water, D-peptides, as well as the larger polypeptide D-proteins, have similar but mirrored properties to the L-peptides and L-proteins with identical sequences. If an L-protein does not require a Chaperone or a structural cofactor to fold, its D-enantiomer protein should have a mirror image conformation with respect to the L-protein (Figure 1). A D-enzyme should act on substrates of reverse chirality compared to the L-enzyme with the same sequence. Similarly, if an L-peptide binds to an L-protein, their D-peptide and D-protein counterparts should bind together in a mirrored way.

D-peptides also have properties that make them attractive as drugs. D-peptides are less susceptible to be degraded in the stomach or inside cells by proteolysis. D-peptide drugs can therefore be taken orally and are effective for a longer period of time. D-peptides are easy to synthesize, when compared to many other drugs. In some cases, D-peptides can have a low immunogenic response.

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