Opioid peptide

Opioid peptides are short-chain peptides that represent the natural binding partners ( ligands ) of the opioid receptors .

Structure and mode of operation

The chemical structure of the opioid peptides is quite different. The peptide chains consist of five ( enkephalins ) to 31 amino acids (beta-endorphins). The folded structures are very similar to the opium alkaloid morphine . The terminal parahydroxy phenyl radical of tyrosine is, for example, similar to the aromatic ring of morphine. The amino acid sequences of the opioid peptides interact with the same receptors as the exogenous opium alkaloids. An essential difference is that the endogenous opioid peptides are broken down again by aminopeptidases immediately after their synthesis . This prevents tachyphylaxis and the development of dependency . The opioid peptides bind to the μ ₁ opioid receptor.

Opioid peptides are involved as transmitters in a large number of biological processes . Alone or together with other transmitter systems, they control physiological processes.

Classification of opioid peptides

There are three main families of endogenous opioid peptides: the enkephalins , the endorphins, and the dynorphins . These three opioid peptides are encoded by three homologous genes in humans . Each of these genes encodes a large protein that is broken down into smaller units - the actual opioid peptides.

Proopiomelanocortin is broken down into beta-endorphin and met-enkephalin
Proenkephalin -A is broken down into different enkephalins
Proenkephalin -B is broken down into dynorphins

Humans ingest further opioid peptides - so-called exorphins - through food, which are broken down into opioid peptides in the body. These are among others:

Casomorphine (used to digest dairy products)
Gluten exorphins such as gliadorphin
Rubiscolin (used to digest spinach leaves )

There are now a number of synthetic opioid peptides such as DAMGO ([D-Ala2, N-MePhe4, Gly-ol] -Enkephalin) or DADLE ([D-Ala2, Leu5] -Enkephalin).

Individual evidence

^ ^A ^b E. Freye: Opioids in medicine. Springer, 2004, ISBN 3-540-40812-6 .

literature

W. Straßburger, E. Friderichs: Ironman, breast milk and toad skin: opioid peptides. In: Pharmacy in our time , 31/2002, pp. 52–8.
E. Oberdisse: Pharmacology and Toxicology. Springer, 2001, ISBN 3-540-41993-4

[freye-1] A ^b E. Freye: Opioids in medicine. Springer, 2004, ISBN 3-540-40812-6 .