Lanthionine

Lanthionine is a naturally occurring, sulfur-containing amino acid that is found in certain proteins. It is a non-proteinogenic amino acid, meaning it is not directly coded for by DNA and does not appear in proteins. Lanthionine is formed by the reaction of two cysteine residues, resulting in the formation of a thioether bridge.

Structure and Properties

Lanthionine is a cyclic amino acid, with a structure that consists of two alanine residues connected by a thioether bridge. This bridge is formed by the replacement of the sulfur atom of one cysteine residue with the methylene group (-CH2-) of another cysteine residue. The resulting structure is highly stable and resistant to degradation by proteases.

The thioether bridge in lanthionine gives it unique properties, including the ability to form stable, cyclic structures. This makes it an important component of certain peptides, including the lantibiotics, a class of antimicrobial peptides.

Biological Role

Lanthionine is a key component of a group of peptides known as lantibiotics. These are a class of antimicrobial peptides that are produced by certain bacteria and have potent activity against a wide range of other bacteria. The lanthionine residues in these peptides contribute to their stability and potency.

In addition to its role in lantibiotics, lanthionine is also involved in the formation of certain proteins in the body. For example, it is a component of the protein keratin, which is found in hair, skin, and nails.

Synthesis

Lanthionine is synthesized in a two-step process. First, two cysteine residues are converted into a dehydroalanine and a cysteine. This is followed by a Michael addition of the cysteine to the dehydroalanine, resulting in the formation of lanthionine.

Medical Significance

Due to its presence in lantibiotics, lanthionine has potential medical significance. Lantibiotics are being investigated for their potential use as antibiotics, particularly in the treatment of drug-resistant bacterial infections.