Isolation, identification, and synthesis of Mas‐MG‐MT I, a novel peptide from the larval midgut of Manduca sexta (lepidoptera: Sphingidae)

A five‐residue myotropic peptide, Manduca sexta midgut myotropin I (Mas‐MG‐MT I), was isolated from an extract of 800 midguts of fifth instar larvae of the tobacco hornworm, Manduca sexta . It was purified by reverse phase and normal phase HPLC. Myotropic activity was screened by a heterologous Locusta migratoria oviduct bioassay. Sequence analysis, amino acid composition analysis, and comparison of candidate synthetic peptides in the amide and acid form revealed the following primary structure: Ala‐Glu‐Pro‐Tyr‐Thr‐NH 2 . This is the first fully identified peptide isolated directly from the midgut of an insect species. Few significant sequence homologies with known vertebrate and invertebrate peptides have been found. © 1995 Wiley‐Liss, Inc.