Characterization of a novel Sepia officinalis neuropeptide using MALDI-TOFMS and post-source decay analysis

A novel neuropeptide acting as a myosuppressor on esophagus, funnel and man tle muscular fibers has been isolated from the stellar ganglia of the mollu sk cephalopod Sepia officinalis by means of HPLC analysis. Fractions were m onitored using a myotropic bioassay. After three separation steps, MALDI-TO F spectrum revealed one main peak at m/z 756.6. The partial N-terminal and C-terminal digestions by exopeptidases followed by MALDI-TOF analysis allow ed the determination of the nature of the two C-terminal and N-terminal ami no acids. Post Source Decay fragmentation of the molecular ion accurately d etermined the following primary sequence: Val-Tyr-Ser-Ala-Pro-Tyr-Gly-OH. T he mapping of this heptapeptide performed in ESI-MS revealed that its distr ibution is restricted to the stellar ganglia, the giant fibers III, and the nervous bundle containing the giant fibers II and the palleal nerve. The n europeptide was not detected in the hemolymph suggesting a release by nerve endings next to the targets. (C) 2001 Elsevier Science Inc. All rights res erved.