van Strien F J, Jenks B G, Heerma W, Versluis C, Kawauchi H, Roubos E W
Department of Animal Physiology, Faculty of Science, University of Nijmegen, The Netherlands.
Biochem Biophys Res Commun. 1993 Feb 26;191(1):262-8. doi: 10.1006/bbrc.1993.1211.
The major N-terminal acetylated endorphin of the pars intermedia of Xenopus laevis was purified and submitted to fast-atom bombardment tandem mass spectroscopy. The collisionally induced dissociation MS/MS spectrum of the [M+H]+ ion revealed sufficient fragment ions to determine unambiguously the identity of the peptide as alpha,N-acetyl beta-endorphin [1-8], the sequence of which was predicted on the basis of the nucleotide sequence of Xenopus POMC cDNA. The determination was confirmed by showing that the synthetic peptide of this structure had identical FAB tandem mass spectrometric characteristics as the endogenous endorphin. We conclude that alpha,N-acetyl beta-endorphin [1-8] is the terminal product of processing of endorphins in the melanotrope cell of Xenopus laevis.
