Identification and tissue mapping of APGWamide-related peptides in Sepia officinalis using LC-ESI-MS/MS

This paper demonstrates for the first time the occurrence of tetrapeptides related to APGWamide in the mollusk cephalopod Sepia officinalis. LC-ESI-MS/MS analysis allowed the identification of the APGWamide-related peptides predicted by the two genes cloned previously in Lymnaea stagnalis and in Mytilus edulis, as well as the dipeptide GWamide released from the processing of the tetrapeptides by a dipeptidyl aminopeptidase (DPAP). TPGWamide and GWamide appeared to be exclusively located in the CNS, and the APGWamide in both the CNS and the nerve endings. The RPGWamide and the KPGWamide were not detected by LC-ESI-MS/MS suggesting they could be totally processed into GWamide. The in vitro processing of the tetrapeptides into GWamide by optic lobe extract revealed a differential processing for each, with APGWamide (44.7%)>RPGWamide(24.3%)>KPGWamide(19.3%)>TPGWamide (11.7%). The tissue mapping results, together with the processing efficiency data suggest that the GWamide is mainly produced from the M. edulis gene products RPGWamide and KPGWamide.