IDENTIFICATION OF SYNAPTIC METABOLITES OF DYNORPHIN-A (1-8) BY ELECTROSPRAY-IONIZATION AND TANDEM MASS-SPECTROMETRY

Synaptic metabolism of the endogenous opioid octapeptide dynorphin (Dy n) A (1-8) (Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile) was studied in vitro upon its incubation with synaptosomes and with synaptosomal plasma membran es isolated from rat brain tissue. Electrospray ionization (ESI) and t andem mass spectrometry were performed using an ion trap instrument, a nd afforded the identification of Dyn A (2-8), Dyn A (1-6) and leucine enkephalin [Dyn A (1-5)] as major metabolites. Preliminary quantitati ve data on the kinetics of Dyn A (1-8) degradation and metabolite form ation was obtained by size-exclusion chromatography/ESI tandem mass sp ectrometry, and revealed an apparent involvement of several enzymes in the metabolism upon incubation with synaptosomes. Predominant formati on of Dyn A (1-6) was observed with the synaptosomal plasma membranes. (C) 1998 John Wiley & Sons, Ltd.