The present invention intends to provide a novel peptide and use thereof. More particularly, the present invention provides a novel peptide and a DNA encoding the same, a drug comprising the peptide or DNA, a screening method/screening kit for a compound or its salt that promotes or inhibits the activity of the peptide, a compound or its salt obtained by the screening, a drug comprising the compound or its salt, etc. The peptide of the invention and the DNA encoding the same are usable, e.g., for the diagnosis, treatment, prevention, etc. of digestive diseases, etc. Moreover, the peptide of the invention is useful as a reagent for screening a compound or its salt that promotes or inhibits the activity of the protein of the invention.