Chapter 64 – FMRFamides

FMRFamide (FMRFa) was originally isolated from mollusks as a cardioacceleratory peptide. This tetrapeptide is observed in any species as similar peptides or N-terminally extended forms. FMRFa is also found in other molluskan species, such as the clam Macrocallista nimbosa and the snails Helix, Aplysia, and Lymnaea. The FMRFa is also present in insects. In the fruit fly Drosophila melanogaster, a prepropeptide encodes 10 copies of FMRFa and FMRFamide-related peptides (FaRPs). D. melanogaster FaRPs share the similar C-terminal sequences, FMRF–NH2. Of 10 FaRPs derived from the prepropeptide, some substitutions and the N-terminally extended forms are observed. FaRPs play roles in the modulation of muscle contraction, including gut contraction and heart rate.