2026-09-21 Posted by TideChem view:73
APGWamide is a short amidated neuropeptide identified in several molluscan species. Its name comes directly from its four-residue sequence: alanine, proline, glycine and tryptophan, followed by a C-terminal amide.
Despite containing only four amino acids, APGWamide participates in complex neuroendocrine signaling. Studies have connected it with neuronal inhibition, muscle relaxation, reproductive behavior and the regulation of male reproductive organs in gastropods.
For researchers, the molecule is also an instructive example of why peptide identity cannot be established by sequence alone. C-terminal amidation, stereochemistry, tryptophan oxidation, counterion content and net peptide concentration can all influence experimental results.
APGWamide is an endogenous molluscan neuropeptide with the sequence:
H-Ala-Pro-Gly-Trp-NH₂
Its abbreviated sequence is:
APGW-NH₂
The terminal “amide” is an essential part of the molecule. APGW-OH, which has a free C-terminal carboxylic acid, is a related but chemically different peptide.
| Property | Value |
| Peptide length | 4 amino acids |
| Sequence | Ala-Pro-Gly-Trp-NH₂ |
| Molecular formula | C₂₁H₂₈N₆O₄ |
| Average molecular weight | Approximately 428.48 g/mol |
| Neutral monoisotopic mass | Approximately 428.217 Da |
| CAS number | 126675-52-3 |
| Peptide class | Amidated molluscan neuropeptide |
The peptide was isolated from the ganglia of the African giant snail Achatina fulica. In that system, it hyperpolarized several neuron types and increased potassium permeability, supporting its classification as an inhibitory neurotransmitter. Original study
Many neuropeptides require C-terminal amidation for full receptor activity. APGWamide belongs to the broader group of Wamide peptides characterized by a terminal tryptophan amide, or Trp-NH₂.
Amidation changes the peptide’s:
Recent receptor studies in Aplysia californica found that the C-terminal Wamide motif is necessary for effective APGWamide receptor activation. Researchers identified three APGWamide-responsive receptors, designated APGWa-R1, APGWa-R2 and APGWa-R3. ACS Chemical Neuroscience
A peptide ordered or synthesized as APGW-OH should not be treated as equivalent to APGW-NH₂ without comparative biological data.
APGWamide and APGWamide-related peptides have been reported across several molluscan groups, including gastropods, bivalves and cephalopods.
Studied species include:
The exact peptide repertoire differs among species. Some molluscs produce related sequences such as RPGWamide, KPGWamide and TPGWamide rather than only APGWamide.
This distinction matters in immunohistochemistry and peptidomics. An antibody described as showing “APGWamide-like immunoreactivity” may recognize several related Wamide peptides. Immunoreactivity alone does not prove that the detected molecule is chemically identical to APGWamide.
Sequence-specific LC-MS/MS or precursor-gene data can provide stronger confirmation.
In Achatina fulica, APGWamide inhibited several identified neurons through membrane hyperpolarization. Electrophysiological evidence indicated an increase in potassium permeability.
This makes APGWamide useful for studying:
The response should not be assumed to be identical across every neuron or molluscan species.
The best-established role of APGWamide is in the regulation of male reproductive behavior in gastropods.
In Lymnaea stagnalis, neurons containing APGWamide become active during eversion of the preputium, a structure involved in male copulation. Experimental APGWamide administration caused relaxation and eversion of the organ. Functional study
Immunohistochemical and in situ hybridization studies have also shown APGWamide-containing neurons and fibers associated with male reproductive tissues in several gastropods. Comparative localization study
In Aplysia, APGWamide-like immunoreactivity has been detected in the central nervous system and in organs involved in sperm storage and transport. Its precursor was predicted to generate nine copies of APGWamide together with several connecting peptides. Aplysia precursor study
These findings support a reproductive role but do not mean that APGWamide performs exactly the same function in every species.
APGWamide and related peptides have been investigated in molluscan muscle and spawning studies.
In oysters, APGWamide was identified in male genital products and triggered repetitive shell closure under the reported experimental conditions. Oyster study
Expression changes have also been observed around spawning cycles in abalone. These findings make APGWamide relevant to comparative endocrinology, aquaculture biology and environmental physiology, although many species-specific mechanisms remain unresolved.
APGWamide has been studied in connection with imposex, the development of male sexual characteristics in female gastropods following exposure to some environmental contaminants.
These studies investigate whether neuroendocrine changes contribute to abnormal reproductive development. They do not establish APGWamide as a universal cause of imposex across species.
APGWamide may be used in:
The peptide remains a research reagent. It is not an approved human or veterinary therapeutic.
APGWamide can be prepared using standard Fmoc solid-phase peptide synthesis. Its short sequence makes chain assembly relatively straightforward, but the C-terminal amide and tryptophan residue require specific attention.
A Rink amide resin or another suitable amide-generating support is typically used. Cleavage from this resin produces the required C-terminal carboxamide.
Using an ordinary acid-generating resin would produce APGW-OH instead.
The peptide is assembled from the C-terminus to the N-terminus:
After each coupling, the Fmoc group is removed before the next residue is introduced.
The completed peptide is cleaved from the resin under acidic conditions. The cleavage system should remove the tryptophan side-chain protection while limiting oxidation and acid-related side reactions.
Appropriate scavengers, controlled reaction time and limited exposure to air and light can help protect the indole side chain.
Crude APGWamide is normally purified by reversed-phase preparative HPLC and then lyophilized.
Although the sequence is short, purification may still need to separate:
Tryptophan is the most obvious chemical stability risk in APGWamide. Oxidation can occur during cleavage, purification, drying or solution storage.
Potential contributors include:
LC-MS can detect several oxidation-related mass shifts, but method development should not rely on only one expected oxidation product.
The Ala-Pro peptide bond may adopt cis and trans conformations. This can create shoulders or multiple chromatographic features even when the covalent structure is unchanged.
Method-development teams should distinguish conformational interconversion from a true chemical impurity. Temperature, solvent composition and chromatographic conditions can influence the observed profile.
Incomplete amidation or use of the wrong resin can generate APGW-OH. The acid and amide differ by approximately 0.984 Da, requiring suitable mass resolution and reference information.
Preparative purification frequently produces a TFA salt. Acetate or another counterion may be requested for biological compatibility, but salt exchange must be analytically confirmed.
Counterion and water can contribute substantially to the mass of a small peptide. For a tetrapeptide, reporting net peptide content is often more informative than reporting only gross powder weight.
A research-grade APGWamide package should normally contain more than an HPLC purity percentage.
RP-HPLC is used to assess peptide purity and related substances. Detection near 214 nm provides general peptide-bond sensitivity, while the tryptophan residue also supports detection near 280 nm.
Purity depends on the analytical method. The certificate should identify:
ESI-MS or MALDI-TOF can confirm molecular mass. For uncharged APGWamide, the calculated neutral monoisotopic mass is approximately 428.217 Da, with a protonated ion near m/z 429.224.
Mass spectrometry does not establish enantiomeric purity and may not quantify the peptide counterion.
Depending on the application, testing may include:
For receptor studies, chemical purity does not replace functional testing. An oxidized or incorrectly amidated product can retain a similar bulk HPLC profile while showing altered biological activity.
| Attribute | Recommended information |
| Sequence | H-Ala-Pro-Gly-Trp-NH₂ |
| Residue configuration | L-Ala, L-Pro and L-Trp |
| C-terminus | Amidated |
| Molecular weight | Approximately 428.48 g/mol |
| Identity | LC-MS or equivalent |
| Purity | Method-defined RP-HPLC result |
| Counterion | Reported and quantified where needed |
| Water | Reported for quantitative applications |
| Peptide content | Preferred for molar preparation |
| Residual solvents | Appropriate to intended use |
| Endotoxin | Application-dependent |
| Storage | Supported by supplier data |
| Intended use | Research use only unless otherwise qualified |
Researchers should avoid ordering only by the abbreviation “APGW.” It does not always show whether the N-terminus is free, whether the C-terminus is amidated or which stereochemistry is required.
APGWamide is generally more stable as a dry, lyophilized material than in solution. Storage instructions should follow product-specific stability data and the certificate of analysis.
Practical controls include:
The tryptophan residue makes light and oxidation studies especially relevant. A solvent that dissolves the peptide rapidly may not be appropriate for long-term storage.
PEGylation is technically possible, but native APGWamide has few selective conjugation sites. The free N-terminal amine is the most obvious attachment point.
Because APGWamide contains only four residues, attaching PEG at the N-terminus can substantially change receptor recognition. The terminal Wamide motif must also be preserved because it is important for receptor activation.
Alternative designs may include:
These are experimental analogues, not established equivalents of native APGWamide. Each design requires receptor-specific potency and stability testing.
For most in vitro neurobiology studies, unmodified APGWamide is likely to provide a clearer biological reference. Half-life extension becomes more relevant in long-duration in vivo or delivery studies.
APGWamide is short, but scale-up is not limited to assembling four residues.
Development teams still need to control:
At larger scale, purification yield may influence cost more than coupling efficiency. Process optimization should focus on crude purity, oxidation control and recovery from preparative chromatography.
If a modified APGWamide is required, the conjugation handle and linker should be selected during route design rather than added after the native synthesis process has been finalized.
Tide Chem publicly describes capabilities in protected and non-natural amino acids, short peptides, peptide fragments, PEG derivatives and custom peptide raw-material development. These capabilities are relevant to APGWamide analogue design and custom synthesis. Tide Chem About Us
Potential project support may include:
Before listing Tide Chem as an APGWamide supplier, buyers should request a project-specific proposal confirming sequence, scale, purity, salt form, analytical package and manufacturing status.
The public product catalogue reviewed for this article did not show a dedicated APGWamide product page. Custom synthesis capability should therefore be confirmed rather than presented as an in-stock product.
Its sequence is Ala-Pro-Gly-Trp-NH₂, abbreviated APGW-NH₂.
It contains four amino acid residues, making it a tetrapeptide.
Its average molecular weight is approximately 428.48 g/mol.
No. It is best known as a molluscan neuropeptide.
Reported functions include inhibitory neuronal signaling and regulation of reproductive behavior and reproductive muscles in several molluscan species. Its role is species- and tissue-dependent.
No. APGW-OH has a free C-terminal carboxylic acid, while APGWamide contains a C-terminal amide.
APGWamide is currently a research peptide. It is not an approved human or veterinary medicine.
RP-HPLC and mass spectrometry provide complementary purity and identity data. Counterion, water and net peptide content may also be needed for quantitative experiments.
Possible causes include impurities, tryptophan oxidation and cis-trans conformations around the Ala-Pro bond. Orthogonal analysis is needed to distinguish them.
APGWamide is a compact molluscan neuropeptide with a clearly defined sequence, H-Ala-Pro-Gly-Trp-NH₂. It is best known for its roles in inhibitory neuronal signaling and the regulation of male reproductive behavior in gastropods.
Its small size simplifies solid-phase assembly but does not remove the need for careful quality control. C-terminal amidation, tryptophan oxidation, stereochemistry, counterion content and net peptide concentration can all affect research results.
Scientists sourcing APGWamide should request method-defined HPLC purity, mass confirmation, clear terminal chemistry and appropriate content data. Modified or PEGylated analogues may support stability and receptor studies, but they should be treated as new research compounds rather than direct substitutes for native APGWamide.