Leucosulfakinin, a sulfated insect neuropeptide with homology to gastrin and cholecystokinin.

A sulfated, myotropic neuropeptide termed leucosulfakinin (Glu-Gln-Phe-Glu-Asp-Tyr(SO3H)-Gly-His-Met-Arg-Phe-NH2) was isolated from head extracts of the cockroach Leucophaea maderae. The peptide exhibits sequence homology with the hormonally active portion of the vertebrate hormones human gastrin II and cholecystokinin, suggesting that these peptides are evolutionarily related. Six of the 11 amino acid residues (55 percent) are identical to those in gastrin II. In addition, the intestinal myotropic action of leucosulfakinin is analogous to that of gastrin.

Consensus chemistry and beta-turn conformation of the active core of the insect kinin neuropeptide family.

BACKGROUND: Neuropeptides are examples of small, flexible molecules that bind to receptors and induce signal transduction, thereby eliciting biological activity. The multifunctional insect kinin neuropeptides retain full activity when reduced to only their carboxy-terminal pentapeptide (Phe1-X2-X3-Trp4-Gly5-NH2), thereby allowing extensive structure-function studies and conformational analysis. RESULTS: A combined experimental and theoretical analysis of the insect kinin carboxy-terminal pentapeptide was used to probe the role of each residue, define the bioactive conformation, and design a constrained bioactive analog. Coupling receptor-binding data with two biological activity assays allowed receptor binding and signal transduction to be differentiated. A preferred beta-turn conformation, found for residues 1-4 by molecular dynamics simulations, was tested by designing a conformationally restricted cyclic hexapeptide. This cyclic analog showed a preference for the beta-turn conformation, as shown by a conformational search and nuclear magnetic resonance spectroscopy, and it showed stronger receptor binding but decreased activity relative to highly active linear analogs. CONCLUSIONS: Each residue of the insect kinin carboxy-terminal pentapeptide has a distinct role in conformational preference, specific receptor interactions or signal transduction. The beta-turn preference of residues Phe1-X2-X3-Trp4 implicates this as the bioactive conformation. The amidated carboxyl terminus, required for activity in many neuropeptide families, may be generally important for signal transduction and its inclusion may therefore be essential for agonist design.

Locustatachykinin I and II, two novel insect neuropeptides with homology to peptides of the vertebrate tachykinin family.

Two myotropic peptides termed locustatachykinin I (Gly-Pro-Ser-Gly-Phe-Tyr-Gly-Val-Arg-NH2) and locustatachykinin II (Ala-Pro-Leu-Ser-Gly-Phe-Tyr-Gly-Val-Arg-NH2) were isolated from brain-corpora cardiaca-corpora allata-suboesophageal ganglion extracts of the locust, Locusta migratoria. Both peptides exhibit sequence homologies with the vertebrate tachykinins. Sequence homology is greater with the fish and amphibian tachykinins (up to 45%) than with the mammalian tachykinins. In addition, the intestinal myotropic activity of the locustatachykinins is analogous to that of vertebrate tachykinins. The peptides discovered in this study may just be the first in a whole series of substances from arthropod species to be identified as tachykinin family peptides. Moreover, both chemical and biological similarities of vertebrate and insect tachykinins substantiate the evidence for a long evolutionary history of the tachykinin peptide family.

Locustatachykinin immunoreactivity in the blowfly central nervous system and intestine.

An antiserum raised against locustatachykinin I, one of four myotropic peptides that have been isolated from the locust brain and corpora cardiaca, was characterized by enzyme-linked immunosorbent assay (ELISA) and used for immunocytochemical detection of neurons and endocrine cells in the nervous system and intestine of the blowfly Calliphora vomitoria. The ELISA characterization indicated that the antiserum recognizes the common C-terminus sequence of the locustatachykinins I-III. Hence, the cross reaction with locustatachykinin IV is less, and in competitive ELISAs no cross reaction was detected with a series of vertebrate tachykinins tested. It was also shown that the antiserum recognized material in extracts of blowfly heads, as measured in ELISA. In high-performance liquid chromatography the extracted locustatachykinin-like immunoreactive (LomTK-LI) material eluted in two different ranges. A fairly large number of LomTK-LI neurons was detected in the blowfly brain and thoracicoabdominal ganglion. A total of about 160 LomTK-LI neurons was seen in the proto-, deuto-, and tritocerebrum and subesophageal ganglion. Immunoreactive processes from these neurons could be traced in many neuropil regions of the brain: superior and dorsomedian protocerebrum, optic tubercle, fan-shaped body and ventral bodies of the central complex, all the glomeruli of the antennal lobes, and tritocerebral and subesophageal neuropil. No immunoreactivity was seen in the mushroom bodies or the optic lobes. In the fused thoracicoabdominal ganglion, 46 LomTK-LI neurons could be resolved. The less evolved larval nervous system was also investigated to obtain additional information on the morphology and projections of immunoreactive neurons. In neither the larval nor the adult nervous systems could we identify any efferent or afferent immunoreactive axons or neurosecretory cells. The widespread distribution of LomTK-LI material in interneurons suggests an important role of the native peptide(s) as a neurotransmitter or neuromodulator within the central nervous system. Additionally a regulatory function in the intestine is indicated by the presence of immunoreactivity in endocrine cells of the midgut.

Differential distribution of pyrokinin-isoforms in cerebral and abdominal neurohemal organs of the American cockroach.

Different pyrokinin isoforms were identified from major neurohemal organs of the American cockroach. During their isolation they were recognized by bioassay using a hyperneural muscle preparation that is sensitive to pyrokinins. All structures were elucidated by sequence analysis and mass spectrometry. The primary structures of the novel peptides isolated from the retrocerebral complex are LVPFRPRL-NH2 (designated Pea-PK-3) and DHLPHDVYSPRL-NH2 (designated Pea-PK-4). A pyrokinin, labeled Pea-PK-5, was isolated from abdominal perisympathetic organs. Structural analysis of this peptide yielded the sequence GGGGSGETSGMWFGPRL-NH2. The threshold concentrations of the identified pyrokinins for an eliciting effect on contractions of the hyperneural muscle preparations differed dramatically. This indicates that the different distribution of pyrokinin-isoform observed in neurohemal organs may be associated with different functions. This is the first report of a differential distribution of peptide-isoforms in the neurohemal organs of insects.

The unique neuropeptide pattern in abdominal perisympathetic organs of insects.

We successfully isolated and identified the abundant neuropeptides of the abdominal perisympathetic organs of the American cockroach, including all myoactive compounds. Peptide sequence analysis and mass spectrometry of abundant substances that were not bioactive in different muscle assays yielded the following sequences: TDPLWQLPGAHLEQYLS-NH2 (Pea-YLS-amide), AFLTLTPGSHVDSYVEA-OH (Pea-VEAacid), and SDLTWTYQSPGDPTNSKN-OH (Pea-SKNacid). The given structures led to the conclusion of an unique neuropeptide pattern in abdominal perisympathetic organs. We confirmed this assumption with immunocytochemical studies, using antisera raised against different myotropic neuropeptides of the abdominal perisympathetic organs. Moreover, mass spectrometric methods, developed for the investigation of single neurohemal organs, confirmed the neuropeptide pattern in these organs.

Silkworm diapause induction activity of myotropic pyrokinin (FXPRLamide) insect neuropeptides.

A family of myotropic neuropeptides sharing the common C-terminal pentapeptide Phe-Xxx-Pro-Arg-Leu-NH2 (Xxx = Ser, Thr, Val), known as the pyrokinins, has been isolated from the cockroach Leucophaea maderae and locust Locusta migratoria of the order Orthoptera. A hormone (Bom-DH) that elicits diapause induction in the silkworm Bombyx mori (order Lepidoptera) also contains this C-terminal pentapeptide (Xxx = Gly). The orthopteran pyrokinin neuropeptides elicit significant diapause-inducing activity in the lepidopteran silkworm. Despite containing the sterically bulky, inflexible Val residue in the variable Xxx position, the locust pyrokinin Lom-PK is threefold more active than native Bom-DH as a diapause induction agent. The C-terminally truncated cockroach leucopyrokinin (LPK) fragment, Thr-Ser-Phe-Thr-Pro-Arg-NH2 [LPK(2-7)], proved virtually inactive in the silkworm assay, demonstrating the importance of an intact C-terminal pentapeptide sequence to diapause induction activity. Bom-DH also elicits significant myostimulatory activity in a cockroach hindgut assay, although at a level several orders of magnitude less than the native myotropic peptide LPK. However, the C-terminal pentapeptide of Bom-DH (Xxx = Gly) is equipotent with the LPK C-terminal pentapeptide (Xxx = Thr) as a myostimulatory agent. The cross-activity observed for the various pyrokinins suggests that the receptors that mediate the disparate physiological processes of diapause in the silkworm and hindgut contraction in the cockroach share homologous features.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural aspects of gastrin/CCK-like insect leucosulfakinins and FMRF-amide.

The leucosulfakinins (LSKs), isolated from head extracts of the cockroach Leucophaea maderae, are sulfated neuropeptides with homology to gastrin and cholecystokinin. The undecapeptide LSK and decapeptide LSK-II stimulate contractions of the isolated cockroach hindgut. Several structural aspects of the two gastrin/CCK-like insect leucosulfakinins (LSKs) and their relation to FMRF-amide are discussed. Replacement of the oxidation sensitive Met residue with isosteric norleucine leads to an analog with retention of biological activity. The Arg residue of the LSKs is critical for cockroach hindgut contractile stimulatory activity, as its introduction into gastrin II transforms the inactive peptide into an active analog. As demonstrated by the equipotent [His14,Arg16]gastrin II, the His8 and Asp5 residues of LSK are not critical for activity. The common C-terminal tetrapeptide of the LSKs ([8-11]LSK) is inactive. Taken together with a comparison of the two LSK structures, the data suggest that the LSK active core resides between [8-11]LSK and [4-11]LSK. This is confirmed by considerable activity displayed by the sulfate analog of LSK-II, which contains an extra sulfate group on the Ser2 residue in the N-terminal region. Homology between the LSKs and molluscan cardioacceleratory and rectum contractile neuropeptide FMRF-amide and Met-enkephalin-Arg6-Phe7 is discussed. The insect LSKs may represent a molecular evolutionary link between the vertebrate gastrin/CCK family and this mammalian enkephalin.

Isolation, characterization and biological activity of a diuretic myokinin neuropeptide from the housefly, Musca domestica.

A competitive ELISA employing a polyclonal antiserum raised against leucokinin-I was used to isolate and purify a myokinin (muscakinin) from 1.05 kg of adult houseflies (Musca domestica). Following solid-phase purification, seven HPLC column steps were used to purify 4.8 nmol of leucokinin-immunoreactive material. Sequence analysis and mass spectrometry were consistent with the structure Asn-Thr-Val-Val-Leu-Gly Lys-Lys-Gln-Arg-Phe-His-Ser-Trp-Gly NH2. This peptide was synthesized and co-eluted with the natural peptide on three different HPLC columns. The activities of natural and synthetic muscakinin were identical, with both producing a 4-5 fold increase in fluid secretion by housefly Malpighian tubules at nanomolar concentrations. The presence of a pair of basic residues (Lys-Lys) suggested muscakinin might be processed further, with the peptide pGlu-Arg-Phe-His-Ser-Trp-Gly NH2 being produced by conversion of an N-terminal glutamine to pyroglutamic acid. However, this analog was 1000-fold less active than the intact peptide, comparable to the activity of AK-V which shares the same C-terminal pentapeptide sequence. The diuretic activity of muscakinin is more than double that of a previously identified CRF-related diuretic peptide (Musca-DP) from the housefly, and the two peptides act synergistically in stimulating fluid secretion. Muscakinin also increased the frequency and amplitude of contractions by housefly hindgut which might further contribute to the excretory process.

Structure-activity relationships for inhibitory insect myosuppressins: contrast with the stimulatory sulfakinins.

Unusual among insect neuropeptides, the decapeptide myosuppressins are capable of inhibiting contractions of visceral muscle, including the isolated cockroach hindgut. The C-terminal pentapeptide Val-Phe-Leu-Arg-Phe-NH2 has been identified as the myosuppressin active core, the minimum number of residues required to elicit hindgut myoinhibitory activity. Activity of the same magnitude as the parent neuropeptide requires the C-terminal heptapeptide fragment Asp-His-Val-Phe-Leu-Arg-Phe-NH2. Evaluation of a series of substitution analogs delineates structural features critical for myoinhibitory activity within this important fragment. The branched, hydrophobic residues in myosuppressin position 6 (Val) and particularly position 8 (Leu), their absence in the myostimulatory sulfakinins, and the different roles played by the shared Asp residue (myosuppressin position 4; leucosulfakinin position 5) in peptide-receptor interaction, account in large degree for the contrasting biological activities elicited by these otherwise structurally similar peptide families. The results may have broad significance for other invertebrate myotropic systems, such as the locust heart and the pharyngeal retractor muscle of the mollusc Helix aspersa.

Isolation, identification, and synthesis of PDVDHFLRFamide (SchistoFLRFamide) in Locusta migratoria and its association with the male accessory glands, the salivary glands, the heart, and the oviduct.

An amidated decapeptide, exhibiting strong inhibitory activity of spontaneous visceral muscle movements, was isolated from 9000 brain-corpora cardiaca-corpora allata-subesophageal ganglion complexes of the migratory locust, Locusta migratoria. During the process of HPLC purifications, the biological activity of the fractions was monitored using the isolated hindgut of the cockroach Leucophaea maderae. The primary structure of this myotropic peptide is Pro-Asp-Val-Asp-His-Val-Phe-Leu-Arg-Phe-NH2 and is identical to SchistoFLRFamide isolated from the grasshopper, Schistocerca gregaria. It shares the carboxy-terminal sequence FLRFamide with several identified peptides from different phyla. At this moment, six decapeptides isolated from different insect species are identical at 7 of the 10 amino acid residues (X-D-V-X-H-X-FLRFamide). The cockroach, fly, and locust peptides differ only by the N-terminal amino acid residue. Synthetic SchistoFLRFamide showed biological as well as chemical characteristics indistinguishable from the native peptide. It provoked a decrease in frequency and amplitude of contractions of the locust oviduct. By means of a polyclonal antiserum directed against the carboxy terminal of SchistoFLRFamide, we demonstrated that the male accessory glands, the heart, the oviduct, and the salivary glands were innervated by axons containing SchistoFLRFamide-like immunoreactivity. Administration of SchistoFLRFamide elicited an immediate effect on the basal membrane potential of the opalescent tubule gland cells.

Relationships between the FMRFamide-related peptides and other peptide families.

The relationships between peptide families are recognized in terms of structural similarity and immunological and biological activity. Most of the currently known FMRFamide-related peptides (FaRPs) of molluscs were tested in a radioimmunoassay (RIA) and in the two standard bioassays for FMRFamide: the radula protractor muscle of the whelk Busycon contrarium, and the isolated heart of the clam Mercenaria mercenaria. Some peptides were also tested on the heart of the snail Helix aspersa. The responses of the different assays to these peptides were generally similar, but substantial diversity precluded an absolute resolution of relationships, even among molluscan FaRPs. Nevertheless, this set of responses does constitute a standard against which to estimate the relative affinities of putative FaRPs from other animal groups. Many of the non-molluscan FaRPs (e.g., the pancreatic polypeptide-related peptides, gastrin/CCK, and the opioid peptides) are relatively inactive on the molluscan assays, but others (e.g., LPLRFamide, a peptide isolated from chicken brain; the opioid receptor-modulating peptides A18Fa and F8Fa; and gamma 1-MSH) were relatively potent. Several arthropod FaRPs have substantial FMRFamide-like sequence similarity and immunoreactivity, and they may be homologous members of the molluscan peptide family. However, those structural and functional aspects of peptide families that transcend phyletic lines probably reflect basic principles of binding between peptides and membrane proteins rather than homology.

A nonpeptidal peptidomimetic agonist of the insect FLRFamide myosuppressin family.

Benzethonium chloride (Bztc) is the first totally nonpeptide ligand for an insect, indeed an invertebrate, peptide receptor. Bztc mimics the inhibitory physiological activity of the myosuppressins, a subfamily of the FLRFamides, in three different insect bioassay systems. The inhibitory action of leucomyosuppressin and the nonpeptide Bztc in both the cockroach hindgut and the mealworm neuromuscular junction can be blocked by the lipoxygenase inhibitor, nordihydroguaiaretic acid, providing evidence for similar modes of action. Lipoxygenase metabolites of arachidonic acid may mediate inhibition of neuromuscular transmission by these two factors. In addition, Bztc competitively displaces a radiolabeled myosuppressin analogue from high- and low-affinity receptors of the locust oviduct. Thus, the nonpeptide interacts with both binding and activating regions of myosuppressin receptors. Molecular dynamics experiments in which selected functional groups of Bztc were fit onto corresponding functional groups of low-energy myosuppressin pentapeptide structures indicate how Bztc may mimic the myosuppressins at a molecular level. The discovery of Bztc as a nonpeptidal peptidomimetic analogue provides an opportunity to develop new pest management strategies by targeting an insect's own peptide receptor.

Potent pheromonotropic/myotropic activity of a carboranyl pseudotetrapeptide analogue of the insect pyrokinin/PBAN neuropeptide family administered via injection or topical application.

A pseudotetrapeptide analogue of the pyrokinin/PBAN or FXPRLamide family (Cbe-Thr-Pro-Agr-Leu-NH2; Cbe = 2-o-carboranylethanoyl-), in which the phenyl ring of the Phe side chain is replaced with the hydrophobic cage-like o-carborane moiety, was synthesized and found to be 10-fold more potent than cockroach leucopyrokinin on an isolated cockroach hindgut bioassay system. In contrast with the naturally occurring peptide, the myostimulatory activity could not be immediately reversed following a saline rinse, providing evidence that the pseudopeptide analogue binds very strongly to the receptor. Once the analogue reaches the receptor, strong receptor binding characteristics may allow it to avoid inactivation by hemolymph peptidases. Although it has an eightfold smaller sequence than the endogenous 33-membered pheromone biosynthesis activating neuropeptide (PBAN), the carboranyl analogue is 10-fold more potent in an in vivo pheromonotropic bioassay of the female tobacco budworm moth Heliothis virescens, demonstrating that the small, C-terminal pentapeptide pyrokinin core analogue contains all the structural information necessary to fully activate pyrokinin receptors. In contrast with PBAN, the amphiphylic carboranyl analogue elicits pheromone production following topical application in aqueous solution to the lateral abdominal surface of H. virescens, providing a noninvasive means of inducing pheromone production in moths. The analogue can potentially serve as a useful tool to insect researchers studying, and/or attempting to disrupt, physiological processes regulated by pyrokinin-like neuropeptides in insects. A possible role for this and related pyrokinin analogues in future pest insect management strategies is briefly discussed.

Primary structure of CHH/MIH/GIH-like peptides in sinus gland extracts from Penaeus vannamei.

Peptides belonging to the CHH/MIH/GIH-family of crustacean hormones were isolated from acetic acid extracts of sinus glands isolated from eyestalks of the shrimp, Penaeus vannamei. The peptides were isolated by chromatography and molecular weights determined by MALDI mass spectrometry. Peptides in the range of 7-9 kDa and containing three disulfide bridges were selected for amino acid sequence analysis. Three peptides with the requisite properties were present in sufficient amounts for sequence analysis. Two peptides had unique sequences similar to CHH/MIH/GIH peptides from other crustaceans. A third peptide seemed to be a truncated form of one of the previous sequences.

Isolation of periviscerokinin-2 from the abdominal perisympathetic organs of the American cockroach, Periplaneta americana.

Using the isolated hyperneural muscle as bioassay, a novel myotropin was isolated from the abdominal perisympathetic organs of Periplaneta americana. This is the second neuropeptide identified from insect perisympathetic organs. Peptide sequence analysis and mass spectrometry yielded the following structure: Gly-Ser-Ser-Ser-Gly-Leu-Ile-Ser-Met-Pro-Arg-Val-NH2. This peptide, named periviscerokinin-2, was confirmed to be amidated by chemical synthesis, bioassay, and comparison of retention times between native and synthetic peptides. A highly specific antiserum was used to determine sites of synthesis in the abdominal ganglia. Besides periviscerokinin-1, periviscerokinin-2 is the only putative myotropic neurohormone from the abdominal perisympathetic organs that is effective in the nanomolar range. This confirms the hypothesis that the neurohormonal system of the ventral nerve cord is remarkably different from that of the brain.

Diuretic activity of C-terminal group analogues of the insect kinins in Acheta domesticus.

A series of insect kinin analogues, AFFPWG-X, modified at the C-terminal group, were evaluated in a cricket Malpighian tubule secretion bioassay. The results were compared with activity profiles observed in a cockroach hindgut myotropic bioassay for these analogues. Although the replacement of the C-terminal amide group with a negatively charged acid leads to a precipitious drop in diuretic activity, it can be partially restored with the introduction of ester groups such as methyl or benzyl. The presence of branched chain character in the C-terminal group or a C-terminal alpha-carbon-amide distance spanning five methylene group spacers is incompatible with the receptor interaction required for biological activity. Significant diuretic activity is retained with four or fewer methylene groups in this region. C-terminal group analogues containing -SCH3, -NHCH2CH2OCH3, or -OCH2(C6H5) offered the greatest retention of diuretic activity while providing increased hydrophobicity and/or steric bulk. The data are of potential value in the development of mimetic analogues of this insect neuropeptide family. Mimetic analogues are potentially valuable tools to insect neuroendocrinologists studying diuresis and/or engaged in the development of future pest management strategies.

Aib-containing analogues of the insect kinin neuropeptide family demonstrate resistance to an insect angiotensin-converting enzyme and potent diuretic activity.

Analogues of the insect kinin family in which the Xaa2 residue of the C-terminal pentapeptide core sequence Phe-Xaa1-Xaa2-Trp-Gly-NH2 (Xaa1 = Asn, His, Phe, Ser, or Tyr; Xaa2 = Ala, Ser, or Pro) is replaced with sterically hindered aminoisobutyric acid (Aib) prove to be resistant to hydrolysis by housefly (Musca domestica) angiotensin-converting enzyme (ACE), an endopeptidase capable of hydrolysis and inactivation of the naturally occurring insect kinin peptides. The Aib residue is compatible with formation of turn in the active core region that is important for the biological activity of the insect kinins. One of the Aib-containing analogues, pGlu-Lys-Phe-Phe-Aib-Trp-Gly-NH2, is five- and eightfold more active than the most active endogenous insect kinins in cockroach (Leucophaea maderae) hindgut myotropic and cricket (Acheta domesticus) Malpighian tubule fluid secretion assays, respectively. As the analogue is blocked at both the amino- and the carboxyl-terminus and resistant to an endopeptidase present in insects, it is better adapted than the endogenous peptides to survive for long periods in the hemolymph. Enzyme-resistant insect kinin analogues can provide useful tools to insect researchers studying the neuroendocrine control of water and ion balance and the physiological consequences of challenging insect with diuretic factors that demonstrate enhanced resistance to peptidase attack. If these analogues, whether in isolation or in combination with other factors, can disrupt the water and/or ion balance they hold potential utility for the control of pest insect populations in the future.

Callitachykinin I and II, two novel myotropic peptides isolated from the blowfly, Calliphora vomitoria, that have resemblances to tachykinins.

Two peptides, related to the locust myotropic peptides locustatachykinin I-IV, were isolated from the blowfly Calliphora vomitoria. Whole, frozen flies were used for extraction with acidified methanol. A cockroach hindgut muscle contraction bioassay was used for monitoring fractions during subsequent purification steps. A series of eight different high performance liquid chromatography column systems was required to obtain optically pure peptides. Two peptides were isolated and their sequences determined by Edman degradation and confirmed by mass spectrometry and chemical synthesis as APTAFYGVR-NH2 and GLGNNAFVGVR-NH2. They were named callitachykinin I and II. The peptides have sequence similarities to the locustatachykinins and vertebrate tachykinins. Both callitachykinins were recognized by an antiserum to locustatachykinin I in enzyme-linked immunosorbent assay (ELISA) tests and callitachykinin II was additionally recognized by an antiserum to the vertebrate tachykinin kassinin, suggesting that immunolabeling of blowfly neurons with these antisera is due to neuronal callitachykinins.

Isolation, identification and synthesis of locustamyotropin (Lom-MT), a novel biologically active insect peptide.

A peptide that stimulates the spontaneous contractions of the hindgut of Leucophaea maderae has been purified from extracts of brain-corpora cardiaca/corpora allata-subesophageal ganglion complexes of 9000 adult Locusta migratoria and was designated locustamyotropin or Lom-MT. The primary structure of this 12 residue peptide has been determined Gly-Ala-Val-Pro-Ala-Ala-Gln-Phe-Ser-Pro-Arg-Leu-NH2. The C-terminal sequence (Phe-Ser-Pro-Arg-Leu-NH2) is identical to the C-terminal pentapeptide of the pheromone biosynthesis activating neuropeptide, recently isolated from Heliothis zea, and is also similar to the C-terminal of leucopyrokinin of Leucophaea. Synthetic Lom-MT showed biological as well as chemical characteristics, indistinguishable from those of native Lom-MT. In locust preparations, Lom-MT provoked an increase in frequency, amplitude and tonus of contractions of the oviduct, but was inactive in the same conditions on the locust hindgut preparation.