A PROENKEPHALIN A-DERIVED PEPTIDE ANALOGOUS TO BOVINE ADRENAL PEPTIDE-E FROM FROG BRAIN - PURIFICATION, SYNTHESIS, AND BEHAVIORAL-EFFECTS

A peptide derived from the posttranslational processing of proenkephal in A was isolated from an extract of the brain of the European green f rog Rana ridibunda and its primary structure established as: Tyr-Gly-G ly-Phe-Met-Arg-Arg-Val-Gly-Arg(10)- p-GIn-Asp-Tyr-Gln-Lys-Arg(20)-Tyr- Gly-Gly-Phe-Met. The structure was confirmed by chemical synthesis. Th e peptide represents an amphibian equivalent of bovine adrenal peptide E [preproenkephalin A (206-230)-peptide] but the sequence contains tw o amino acid substitutions (Met(15) --> Gln and Leu(25) --> Met) compa red with the mammalian peptide. The data support previous hypotheses t hat the Leu-enkephalin sequence is not present in preproenkephalin A o f amphibians. Intracerebroventricular injections of frog peptide E (10 and 100 ng) in mice had no significant effect on horizontal locomotor activity. The peptide, in doses up to 1 mu g, had no effect on latenc y of escape jumping in the hot plate test and the peptide (100 ng) did not modify responses (paw licking, rearing, and escape jumping) in mo rphine-treated mice. Copyright (C) 1996 Elsevier Science Inc.