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Cetrorelix acetate is a synthetic decapeptide antagonist of the gonadotropin-releasing hormone receptor. Unlike GnRH agonists, it inhibits receptor activation through direct competition with GnRH rather than first stimulating the receptor and relying on subsequent desensitization.
Its sequence incorporates multiple D-amino acids and non-proteinogenic residues designed to create high-affinity receptor binding without productive receptor activation.
Product Information
| Property | Specification |
|---|---|
| Product Name | Cetrorelix Acetate |
| CAS No. | 130143-01-0 |
| Condensed Sequence | Ac-D-2Nal-D-Phe(4-Cl)-D-3Pal-Ser-Tyr-D-Cit-Leu-Arg-Pro-D-Ala-NH₂ |
| Peptide Length | 10 amino-acid residues |
| Peptide Formula | C70H92ClN17O14 |
| Peptide Moiety Molecular Weight | Approximately 1431.0 Da |
| Reference Acetate Form | Diacetate |
| Reference Diacetate Formula | C74H100ClN17O18 |
| Reference Diacetate Molecular Weight | Approximately 1551.2 Da |
| N-Terminus | Acetylated |
| C-Terminus | D-Ala-NH₂ |
| Primary Target | GnRH receptor / GNRHR |
| Pharmacological Role | Competitive GnRH receptor antagonist |
A Heavily Engineered Antagonist Sequence
Cetrorelix differs substantially from native GnRH. Its N-terminal region contains D-2Nal, 4-chloro-D-Phe and D-3Pal, introducing bulky aromatic and heteroaromatic side chains into positions important for receptor recognition.
The sequence also contains D-Cit6 and D-Ala10 together with N-terminal acetylation and C-terminal amidation.
These modifications create a peptide optimized for receptor occupancy without inducing the same active receptor conformation produced by GnRH agonists.
Competitive Blockade Without Agonist Pretreatment
Cetrorelix competes with endogenous GnRH for the pituitary receptor and inhibits downstream gonadotropin signaling in a concentration-dependent manner.
Because its mechanism is antagonistic, receptor blockade does not require an initial phase of agonist stimulation or prolonged receptor desensitization.
This distinction makes Cetrorelix useful for experiments where researchers need relatively direct interruption of GnRH-dependent signaling.
Antagonist Binding and Receptor Conformation
Mutagenesis studies of the human GnRH receptor indicate that agonists and peptide antagonists occupy overlapping but non-identical interaction networks within the receptor-binding pocket.
The bulky hydrophobic N-terminal residues of Cetrorelix contribute to receptor binding while failing to stabilize the active G-protein-coupled receptor conformation characteristic of agonist ligands.
Additional studies have also shown that Cetrorelix can influence receptor internalization behavior, illustrating that peptide antagonism can involve more than simple steric competition.
Cetrorelix Versus GnRH Agonists
| Feature | Cetrorelix | GnRH Agonists |
|---|---|---|
| Primary Action | Competitive receptor blockade | Receptor activation |
| Initial Agonist Signaling | Not required | Present |
| Long-Term Suppression Mechanism | Continued antagonist occupancy | Desensitization/down-regulation |
| Sequence Type | Highly modified decapeptide | Modified GnRH agonist scaffold |
Experimental and Quality Considerations
Cetrorelix contains several non-standard amino-acid residues, making molecular identity particularly important. Correct stereochemistry, chlorinated phenylalanine, pyridylalanine and citrulline incorporation should be considered together with purity.
Our Peptide Quality Control capabilities support LC-MS and analytical HPLC according to the selected specification.
Custom antagonist substitutions or GnRH-derived analogs can be evaluated through Chemical Peptide Synthesis.
Frequently Asked Questions
Is Cetrorelix an agonist or antagonist?
Cetrorelix is a competitive GnRH receptor antagonist.
Does Cetrorelix require receptor desensitization before blocking GnRH signaling?
No. It directly competes with GnRH for receptor binding.
Why does the sequence contain several D-amino acids?
D-stereochemistry and non-natural side chains help create a receptor-binding geometry and stability profile distinct from native GnRH.