Binding studies of novel, non-mammalian enkephalins, structures predicted from frog and lungfish brain cDNA sequences

E. Bojnik, A. Magyar, G. Tóth, S. Bajusz, A. Borsodi, S. Benyhe

Research output: Contribution to journalArticle

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Abstract

Leu- and Met-enkephalin were the first endogenous opioid peptides identified in different mammalian species including the human. Comparative biochemical and bioinformatic evidence indicates that enkephalins are not limited to mammals. Various prodynorphin (PDYN) sequences in lower vertebrates revealed the presence of other enkephalin fingerprints in these precursor polypeptides. Among the novel enkephalins Ile-enkephalin (Tyr-Gly-Gly-Phe-Ile) was primarily observed in the African clawed frog (Xenopus laevis) PDYNs, while the structure of Phe-enkephalin (Tyr-Gly-Gly-Phe-Phe) was predicted by analyzing brain cDNA sequences encoding a PDYN of the African lungfish (Protopterus annectens). Ile-enkephalin can also be found in the PDYNs of four other fish species including the eel, bichir, zebrafish and tilapia, but no further occurrence for the Phe-enkephalin motif is available as yet. Based on sequencing data, the biological relevance of Phe- and Ile-enkephalin is suggested, because both of them can arise by regular posttranslational enzymatic processing of the respective neuropeptide precursors. In various receptor binding assays performed on rat brain membrane preparations both of the new peptides turned out to be moderate affinity opioids with a weak preference for the δ-opioid receptor (DOP) sites. Phe-enkephalin of the lungfish displayed rather unexpectedly low affinities toward the μ-opioid receptor (MOP) and DOP, while exhibiting moderate affinity toward the κ-opioid receptor (KOP). In receptor-mediated G-protein activation assays measured by the stimulation of [35S]GTPγS binding, Met-enkephalin produced the highest stimulation followed by Leu-enkephalin, Ile-enkephalin and Phe-enkephalin, whereas the least efficacious among these endogenous peptides was still more effective than the prototype opiate agonist morphine in these functional tests.

Original languageEnglish
Pages (from-to)867-874
Number of pages8
JournalNeuroscience
Volume158
Issue number2
DOIs
Publication statusPublished - Jan 23 2009

Fingerprint

Enkephalins
Anura
Complementary DNA
Brain
Opioid Receptors
Leucine Enkephalin
Methionine Enkephalin
Peptides
Opiate Alkaloids
Tilapia
Eels
Opioid Peptides
Xenopus laevis
Dermatoglyphics
Zebrafish
Computational Biology
Neuropeptides
GTP-Binding Proteins
Morphine
Opioid Analgesics

Keywords

  • opioid receptors
  • prodynorphin
  • proenkephalin
  • Protopterus
  • rat brain
  • Xenopus

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

Binding studies of novel, non-mammalian enkephalins, structures predicted from frog and lungfish brain cDNA sequences. / Bojnik, E.; Magyar, A.; Tóth, G.; Bajusz, S.; Borsodi, A.; Benyhe, S.

In: Neuroscience, Vol. 158, No. 2, 23.01.2009, p. 867-874.

Research output: Contribution to journalArticle

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