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This paper reports the purification of a tachykinin isoform from the midgut of the desert locust, Schistocerca gregaria. One hundred locust midguts were extracted in an acidified methanolic solvent, after which three HPLC column systems were used to obtain a pure peptide. A tachykinin immunoassay was used to monitor all collected fractions. After each purification step the purity of the sample was monitored by MALDI-TOF mass spectrometry. The pure peptide was sequenced by ESI-Qq-oa-TOF mass spectrometry. Ed-man degradation-based automated microsequencing and chemical synthesis confirmed the sequences. The midgut peptide, GNTKKAVPGFYGTRamide (Scg-midgut-TK), belongs to the tachykinin family with identified members in all vertebrate phyla and some invertebrate phyla: arthropods, annelids and molluscs. Scg-midgut-TK is the first tachykinin purified from midguts of the desert locust Schistocerca gregaria. In comparison to locust brain tachykinins, the midgut tachykinin is N-terminally extended. Similar to neuropeptide gamma, an N-terminally extended mammalian tachykinin, first isolated from rabbit intestine, the present identified locust intestinal tachykinin contains a putative dibasic cleavage site. (C) 1999 Academic Press.