Molecular Identity and Copper Coordination
GHK-Cu (glycyl-L-histidyl-L-lysine copper(II); CAS 49557-75-7; MW = 340.38 g/mol as free base) is a naturally occurring tripeptide-copper(II) complex first isolated from human plasma albumin by Pickart and Thaler in 1973 (Pickart & Thaler, 1973, Nat New Biol). GHK was subsequently identified as the Cu²⁺-binding N-terminal sequence of human serum albumin, which is the primary copper transporter in plasma, accounting for ~60–70% of plasma copper under physiological conditions. All research described is for scientific, laboratory purposes only. Not for human use.
The GHK tripeptide coordinates Cu²⁺ through a square-planar geometry: the glycine α-amino nitrogen, deprotonated glycyl-histidyl amide nitrogen, histidine imidazole Nδ1, and a fourth ligand (either the histidine backbone carbonyl or a water molecule, depending on solution conditions) form a 4N planar coordination sphere (Perkins et al., 1999, J Am Chem Soc). This coordination geometry is characteristic of type 2 (non-blue) copper sites and places the Cu²⁺/Cu⁺ redox couple at approximately +0.1 V vs. NHE — within the range relevant to biological oxidation-reduction reactions. The stability constant (log K) for GHK·Cu²⁺ complex formation is approximately 16.4, reflecting high affinity that enables competitive copper acquisition from low-affinity plasma pools under physiological copper concentrations (1–2 µM total plasma copper).
Copper Redox Chemistry and Reactive Oxygen Species
Free copper ions catalyze Fenton-type reactions: Cu²⁺ + O₂•⁻ → Cu⁺ + O₂ (reduction); Cu⁺ + H₂O₂ → Cu²⁺ + •OH + OH⁻ (Haber-Weiss-type). Hydroxyl radical (•OH) is among the most reactive oxidants in biology, capable of abstraction from DNA sugar-phosphate backbones and lipid peroxidation chain initiation. The coordination of Cu²⁺ within GHK's 4N square-planar geometry modulates this redox reactivity: chelated copper demonstrates substantially reduced Fenton activity compared to aquo-Cu²⁺, providing research context for why copper transport proteins universally avoid free Cu²⁺ ions. Conversely, the controlled redox activity of GHK·Cu may participate in superoxide dismutase (SOD)-mimetic chemistry under certain conditions (Cangul et al., 2021, Int J Mol Sci).
Transcriptomic Profiling Studies
Pickart, Margolina, and colleagues conducted high-throughput Affymetrix microarray transcriptomic analysis of GHK-Cu effects in human fibroblast cultures, with key findings published in a series of papers (Pickart et al., 2012, J Biomater Sci Polym Ed; Pickart & Margolina, 2018, Biomolecules). Differential gene expression analysis identified approximately 4,000 genes significantly altered at 1–10 µM GHK-Cu concentrations, with enrichment analysis revealing coordinated regulation of gene ontology (GO) terms including:
- Extracellular matrix organization: Upregulation of COL1A1, COL1A2 (type I procollagen), COL3A1 (type III collagen), COL4A1/A2 (basement membrane), COL7A1 (anchoring fibrils), MMP-2, MMP-9, and TIMP-1/2 — suggesting GHK-Cu modulates the balance between collagen synthesis and MMP-mediated remodeling.
- Angiogenic signaling: VEGFA, VEGFC, FGF1, FGF7, HGF, and angiopoietin-1 (ANGPT1) were among upregulated transcripts, with VEGFR-2 (KDR) showing concomitant upregulation in endothelial cell research models.
- Antioxidant defense: SOD1, SOD2, CAT, GPX1, and HMOX1 (heme oxygenase-1; regulated by NRF2/ARE pathway) were upregulated, consistent with an oxidative stress–adaptive transcriptional response.
- Anti-inflammatory gene network: Downregulation of IL-1β, IL-6, TNF, CXCL8, and NF-κB target genes (VCAM-1, ICAM-1) was observed, paralleling IκBα protein stabilization in some experimental conditions.
Pathway enrichment analysis using KEGG and Reactome databases implicated GHK-Cu in PI3K-AKT, MAPK, and Wnt/β-catenin signaling networks, though the upstream molecular sensor(s) through which GHK-Cu initiates transcriptional changes remain incompletely characterized.
SP1 and AP-1 Transcription Factor Binding
Bioinformatic analysis of promoters from GHK-Cu upregulated genes revealed significant enrichment of Sp1 (GC-box: GGGCGG) and AP-1 (TGA(C/G)TCA) binding motifs. Sp1 is a ubiquitous zinc-finger transcription factor activated by mitogen-stimulated phosphorylation via CDK2 and CK2; it is particularly enriched at TATA-less promoters of housekeeping and extracellular matrix genes including COL1A1 and COL4A1. AP-1 complexes (Fos/Jun heterodimers) are activated by the MAPK cascade downstream of growth factor receptors and integrin signaling (JNK→c-Jun Ser63/73 phosphorylation; ERK1/2→Elk-1→c-Fos induction). The enrichment of these motifs suggests GHK-Cu may act upstream of MAPK/ERK or through direct stabilization of Sp1-DNA complexes, possibly mediated by copper-dependent modulation of chromatin-associated Cu/Zn-SOD activity altering local redox state at accessible chromatin loci (Pickart & Margolina, 2018).
Collagen Synthesis Pathway Research
Type I collagen (the predominant structural protein of dermis, bone, and tendons) is encoded by COL1A1 and COL1A2 genes transcribed as preprocollagen α1 and α2 chains. Post-translational processing involves:
- Signal peptide cleavage in ER lumen
- Prolyl 4-hydroxylase (P4H/LEPRE1) hydroxylation of Pro residues at Xaa-Pro-Gly triads (requires Cu²⁺ as cofactor)
- Lysyl hydroxylase (PLOD1-3) hydroxylation of Lys residues
- Glycosylation of Hyl (hydroxylysine) by COLGALT1/2
- Triple helix assembly of two α1 and one α2 chains → procollagen
- Procollagen N/C proteinase cleavage → collagen
- Lysyl oxidase (LOX, requires Cu²⁺ cofactor) cross-linking → insoluble fibril
Both P4H and LOX require Cu²⁺ as enzymatic cofactor, suggesting that GHK-Cu's copper-chelation activity may serve a specific function in delivering Cu²⁺ to these collagen biosynthetic enzymes. Research by Kagan and Li demonstrated that LOX activity correlates with copper availability, and GHK has been proposed as a high-affinity copper donor to pericellular LOX enzyme in the extracellular matrix microenvironment (Kagan & Li, 2003, J Cell Biochem).
In Vitro Wound Research Models
GHK and GHK-Cu have been studied extensively in scratch-wound fibroblast migration assays. At concentrations of 1–100 ng/mL, GHK-Cu stimulates directed migration at rates 150–200% of vehicle controls in human dermal fibroblast (HDF) monolayer wound models, with maximal effects at approximately 10 ng/mL in multiple independent studies (Pickart et al., 2012). Migration is PI3K-dependent (sensitive to wortmannin/LY294002) and requires actin polymerization (cytochalasin D-sensitive), implicating PI3K→PIP3→Rac1→Arp2/3 as a proximal mediator of the observed cytoskeletal response.
Analytical Characterization of GHK-Cu Research Material
Commercially available GHK-Cu for research use typically presents as a blue-green powder or solution, reflecting the d→d electronic transition of square-planar Cu²⁺ coordination. Quality research material is characterized by:
- HPLC purity ≥98% (UV at 214 nm for peptide bond absorbance; Cu²⁺ complex may require chelation with EDTA prior to reversed-phase analysis to disrupt metal-induced aggregation)
- MS confirmation: [M+H]⁺ = 341.1 for GHK free tripeptide; GHK-Cu complex [M+Cu-2H]⁺ = 400.1
- ICP-MS or atomic absorption spectrophotometry to confirm stoichiometric copper loading (1:1 Cu:peptide)
View Iron All Day's GHK-Cu product listing for full COA documentation including HPLC trace and mass spectrum.
Disclaimer: For research purposes only. Not for human consumption. All products are sold strictly for laboratory use. These statements have not been evaluated by the FDA.