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GHK-Cu vs AHK-Cu: what one amino acid changes
Published October 9, 2026 · Facts checked October 9, 2026
Short answer
GHK-Cu and AHK-Cu are the copper(II) complexes of two tripeptides that differ only in their first amino acid: glycine in GHK, alanine in AHK. Both have histidine in position 2, the Xxx-His motif that holds copper. The extra methyl group makes the neutral 1:1 AHK-Cu complex about 14 g/mol heavier (415.94 against 401.91 g/mol), so its theoretical copper content is a little lower: 15.28 % against 15.81 %.
Side by side
| GHK-Cu | AHK-Cu | |
|---|---|---|
| Peptide sequence | Gly-His-Lys (GHK) | Ala-His-Lys (AHK) |
| Also listed as | Copper Tripeptide-1, prezatide copper | Copper Tripeptide-3 |
| Peptide without copper | C14H24N6O4, 340.38 g/mol | C15H26N6O4, 354.41 g/mol |
| Neutral 1:1 copper complex | C14H22CuN6O4, 401.91 g/mol | C15H24CuN6O4, 415.94 g/mol (calculated: AHK + Cu − 2 H) |
| Theoretical copper, pure 1:1 | 15.81 % | 15.28 % |
| CAS of the copper complex | 89030-95-5 | 767286-83-9 (682809-81-0 is a hydrochloride record) |
| PubChem record of the complex | CID 165429100 | CID 169450582 |
| Strengths per vial we list | 50 mg, 100 mg | 20 mg, 50 mg, 100 mg |
| Used in our copper blends | Yes: GLOW, KLOW, the 50 mg blend | No |
Sources: PubChem CID 73587 · PubChem CID 165429100 · PubChem CID 71587328 · PubChem CID 7408502 · PubChem CID 169450582 · PubChem CID 168431292
Where the difference sits
The first residue of each tripeptide carries the free N-terminal amine. Glycine has a single hydrogen as its side chain; alanine has a methyl group. Histidine in position 2 and lysine in position 3 are the same in both.
Peptides with histidine second in the chain form the Xxx-His group of N-terminal copper(II) binding motifs, known for high-affinity complexes. GHK and AHK are both in that group, which is why the two count as close relatives rather than unrelated materials.
Sources: Gonzalez et al., Chemistry 2018 · PubChem CID 73587 · PubChem CID 7408502
How the copper sits — and what is measured for which
For GHK, NMR, EPR and later work put copper(II) between the N-terminal amine, the deprotonated Gly–His amide nitrogen and the histidine ring, with an oxygen completing a square-planar site. At pH 7.4 one copper binds per peptide, with a conditional dissociation constant of 7.0 × 10⁻¹⁴ M.
Those binding constants and structures were measured on GHK. For AHK the sources cited here establish the shared Xxx-His motif, not a separate set of numbers, so this page does not quote any.
Sources: Laussac et al., Biochem J 1983 · Schirer et al., J Biol Inorg Chem 2017 · Trapaidze et al., J Biol Inorg Chem 2012 · Gonzalez et al., Chemistry 2018
What changes when you read a COA
- MS identity tells them apart: the free peptides differ by about 14 g/mol (340.38 against 354.41).
- The ceiling for copper differs: 15.81 % for pure 1:1 GHK-Cu, 15.28 % for pure 1:1 AHK-Cu. As-is results sit below both because of acetate and water.
- For the Cu²⁺ : peptide ratio, divide copper by 63.546 and peptide content by the free-peptide mass of the right peptide — 340.38 for GHK, 354.41 for AHK.
- Check which CAS a document quotes: 767286-83-9 resolves to the AHK copper complex, 682809-81-0 to a hydrochloride record.
Sources: PubChem CID 73587 · PubChem CID 7408502 · PubChem CID 169450582 · PubChem CID 168431292
What they share in our catalogue
Both come as lyophilized powder in sealed glass vials, ten vials of one strength to a kit, orderable from a single kit, and every batch has its own COA reporting HPLC purity, MS identity, bacterial endotoxin and fill. Copper content and the Cu²⁺ : peptide ratio can be requested before the quote.
Questions
- What is the difference between GHK-Cu and AHK-Cu?
- The first amino acid: glycine in GHK-Cu, alanine in AHK-Cu. The neutral 1:1 AHK-Cu complex is about 14 g/mol heavier, 415.94 against 401.91 g/mol.
- Do GHK-Cu and AHK-Cu bind copper the same way?
- Both have histidine in position 2, the Xxx-His motif that binds copper(II). The detailed binding-site and affinity studies cited here were done on GHK.
- Which contains more copper by weight?
- GHK-Cu, slightly: 15.81 % for the pure 1:1 complex against 15.28 % for AHK-Cu, because AHK is the heavier peptide.
- What CAS number does AHK-Cu have?
- 767286-83-9 resolves to the AHK copper complex in PubChem. 682809-81-0, which some suppliers quote, resolves to a hydrochloride record.
References
- PubChem CID 73587 — glycyl-L-histidyl-L-lysine (C14H24N6O4, 340.38) — GHK identity, formula and molecular weight
- PubChem CID 165429100 — GHK copper complex (C14H22CuN6O4, 401.91) — formula and molecular weight of the neutral 1:1 complex
- PubChem CID 71587328 — prezatide copper (CAS 89030-95-5) — CAS 89030-95-5 belongs to the copper complex; PubChem records it as the singly protonated form, 402.92 g/mol
- PubChem CID 7408502 — L-alanyl-L-histidyl-L-lysine (C15H26N6O4, 354.41) — AHK formula and molecular weight
- PubChem CID 169450582 — AHK copper complex (CAS 767286-83-9) — CAS 767286-83-9 resolves to the AHK copper-complex record
- PubChem CID 168431292 — AHK copper complex, hydrochloride (CAS 682809-81-0) — CAS 682809-81-0 resolves to a hydrochloride record, not to the neutral complex
- Gonzalez et al., Chemistry 2018 — N-terminal Cu-binding motifs (Xxx-His, Xxx-Zzz-His) — Xxx-His peptides such as GHK form high-affinity Cu(II) complexes
- Laussac et al., Biochem J 1983 — NMR and EPR of copper(II)–GHK — three nitrogens and one oxygen around Cu(II), square-planar, pH 6.0–9.6
- Schirer et al., J Biol Inorg Chem 2017 — copper and zinc binding to GHK and DAHK — Cu(II) bound by the N-terminus, the deprotonated amide and histidine Nπ
- Trapaidze et al., J Biol Inorg Chem 2012 — Cu²⁺ binding to DAHK and GHK by ITC — 1:1 stoichiometry; conditional Kd 7.0 × 10⁻¹⁴ M at pH 7.4
Products and related guides
- GHK-Cu vials and fact table
- AHK-Cu vials and fact table
- GHK-Cu molecular weight and CAS
- Why is GHK-Cu blue?