If you have been reading about Endogenous peptide and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-07-23. Numbers and descriptions here follow the published literature rather than marketing material.
Endogenous GHK occurs in blood plasma, saliva, and urine, and reported plasma concentrations decline with age in several studies. Researchers have proposed that the peptide acts as a copper carrier that delivers the metal to cells and to sites of injury. That transport role is a hypothesis supported by binding measurements and tissue-distribution data rather than a settled mechanism, and the peptide is generally described as a minor contributor to total plasma copper transport. Values reported in wound fluid and certain tissue extracts are higher than in circulating plasma.
The sequence carries three residues in the order glycine, histidine, lysine, which places a small, flexible chain around a single metal centre. Compared with larger copper-binding proteins, the complex is compact and its coordination chemistry can be reproduced with synthetic peptide in a laboratory. Published structural work agrees on the nitrogen donor set but differs in the exact geometry assigned under some conditions, so the arrangement is best treated as well characterised in outline rather than fixed in every detail.
GHK-Cu is a coordination complex formed between the tripeptide glycyl-L-histidyl-L-lysine and a copper(II) ion. The peptide was isolated from human plasma in the early 1970s by Loren Pickart, who observed that a plasma fraction from young donors stimulated growth in cultured liver cells. The copper-bound form is abbreviated GHK-Cu, while the metal-free peptide is written simply as GHK. In the research literature the complex also appears as copper tripeptide-1 and as glycyl-histidyl-lysine copper complex.
Research interest in GHK-Cu centers on its ability to deliver copper and to influence cellular processes in laboratory models. In cell culture and animal studies, the complex has been linked to collagen synthesis, antioxidant enzyme activity, and expression of genes associated with tissue remodeling. These effects are not equivalent to proven clinical outcomes. The mechanisms proposed include copper transfer to cuproenzymes, modulation of growth factor signaling, and interactions with extracellular matrix components. How much of the observed activity depends on intact GHK-Cu versus free copper or free peptide is not fully resolved.
The compound entered scientific literature in the 1970s, when plasma factors with copper-binding activity were isolated and characterized. Later work expanded into wound healing, skin biology, and cosmetic formulation, where copper tripeptide-1 became a recognized ingredient name. Most published studies remain preclinical or small-scale, and findings are often reported in specialized dermatology or peptide journals. Regulatory treatment varies: some jurisdictions allow it as a cosmetic ingredient, while research-grade material is sold for laboratory use. Questions about optimal delivery, target tissues, and long-term effects continue to be investigated rather than settled.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Copper(II)-tripeptide complex | One peptide ligand with one coordinated metal centre |
| Peptide sequence | Gly-His-Lys | Three residues written in one-letter notation |
| Free peptide mass | 340.4 g/mol | Metal-free GHK; the complex has a higher mass |
| Appearance | Blue to violet solid or solution | Colour originates from copper d orbital transitions |
| Storage | Desiccated, -20 °C, protected from light | Dry powder is more stable than dissolved material |
Characterizing GHK-Cu requires methods that distinguish the intact complex from free peptide and unbound copper. UV-visible absorption around 600 nm provides a rapid check for copper coordination, while circular dichroism reports on peptide secondary structure. Mass spectrometry confirms the peptide mass and can detect copper adducts under carefully controlled conditions. Electron paramagnetic resonance is particularly informative for Cu(II) because it reveals the ligand field symmetry. No single technique fully defines the complex, so laboratories combine orthogonal methods.
Stability of GHK-Cu in solution depends on pH, temperature, buffer composition, and oxygen exposure. The copper center can undergo reduction or dissociation, especially in the presence of strong metal chelators such as EDTA. Aqueous solutions are often prepared fresh or stored frozen to limit degradation. Lyophilized solid is more stable than liquid formulations, but it can absorb moisture and should be kept dry. Light exposure may also affect copper complexes, though the effect is often modest.
Stability depends on temperature, light exposure, moisture, and the presence of oxidizing or reducing agents. Solid material held dry and protected from light is generally more stable than aqueous solutions, which can undergo gradual degradation. Recommended storage in much of the literature is a freezer at around minus twenty degrees Celsius for long-term retention, with working aliquots kept cold and shielded from light. Repeated freeze-thaw cycles and alkaline pH are commonly noted as factors that accelerate loss of the intact complex, though exact degradation rates vary.
Analytical confirmation usually combines a separation method with a copper-specific measurement. Liquid chromatography or mass spectrometry establishes peptide identity and purity, while an elemental measurement quantifies the metal content. A frequent misconception is that any blue solution contains an intact copper peptide complex; color alone does not confirm structure, because free copper salts and degraded mixtures can also appear colored. Literature on efficacy is mixed, with in vitro findings often more dramatic than human evidence, and reviews note small sample sizes and short follow-up. Open questions include optimal concentration, skin penetration, and long-term effects.
Proposed mechanisms for copper peptide activity center on delivery of copper ions to cells and on peptide fragments acting as signaling molecules. Copper is a cofactor for enzymes involved in collagen cross-linking and antioxidant defense, and the peptide may improve its availability at target sites. Separately, the tripeptide and its breakdown products have been reported to influence gene expression in cultured fibroblasts. Much of this evidence comes from laboratory cell cultures and animal models rather than controlled human trials. The relative contribution of the copper ion and the peptide sequence is therefore not fully settled.
Intracellular Ang II is generated within cardiac cells either through internalization of circulating Ang II or by intracellular synthesis via non-secreted renin and angiotensinogen. Unlike its extracellular counterpart, intracrine Ang II does not rely on traditional cell surface receptors; instead, it binds to nuclear AT1 receptors, modulating gene transcription and intracellular signaling pathways. Studies have demonstrated that intracrine Ang II localizes to the nucleus and mitochondria of cardiac myocytes, where it influences cellular metabolism, oxidative stress, and calcium homeostasis. Additionally, intracellular Ang II has been shown to enhance the transcription of genes involved in hypertrophy and fibrosis, contributing to pathological cardiac remodeling.
White Rhodesian officers and non-commissioned officers left the colony in September and October 1939 to command units of black Africans in the west and east of the continent, with most joining the Royal West African Frontier Force (RWAFF) in the Colony of Nigeria, the Gold Coast and neighbouring colonies. The deployment of white Rhodesian officers and NCOs to command black troops from elsewhere in Africa met with favour from the military leadership and became very prevalent.
Usually, PMR only affects adults over the age of 50. The average age of a person who has PMR is about 70 years old, with the highest prevalence in those older than 70. Women are three times as likely to get PMR as men. People of Western and Northern European descent are more likely to get this disease. It is more likely to affect people of Northern European origin; Scandinavians are especially vulnerable. About 50% of people with temporal arteritis also have polymyalgia rheumatica.
The most medically important species of snake bites in Central Asia is the Caspian cobra (Naja oxiana). It is the most venomous species of cobra in the world, slightly ahead of the Philippine cobra based on a toxinological study from 1992 found in the Indian Journal of Experimental Biology, in which this species produced the highest potency venom among cobras. The venom of this species has the most potent composition of toxins found among any cobra species known. It is made up of primarily highly potent neurotoxins but it also has cytotoxic activity (tissue-death, necrosis) and cardiotoxins. Two forms of "cytotoxin II" (cardiotoxin) were found in the venom of this species. The crude venom of this species produced the lowest known lethal dose (LCLo) of 0.005 mg/kg, the lowest among all cobra species, derived from an individual case of poisoning by intracerebroventricular injection. According to Brown (1973), the subcutaneous LD99–100 value is 0.4 mg/kg, while Ernst and Zug et al. list a value of 0.21 mg/kg SC and 0.037 mg/kg IV. Latifi (1984) listed a subcutaneous value of 0.2 mg/kg (0.09–0.26 mg/kg). In another study, where venom was collected from a number of specimens in Iran, the Subcutis LD50 in lab mice was 0.078 mg/kg. Average venom yield per bite for this species is between 75 and 125 mg (dry weight), but it may yield up to 590 mg (dry weight) in a single bite. The bite of this species may cause severe pain and swelling, along with severe neurotoxicity.
Sources: en.wikipedia.org
According to Rebecca Rocchi et al., 2024, creating natto by using Bacillus subtilis to ferment boiled red lentils, chickpeas, or green peas produced greater amounts of MK-7 than creating natto by using Bacillus subtilis to ferment boiled soybeans, lupins, or brown beans. Food frequency questionnaire-derived estimates of relative intakes of vitamins K in one northern European country suggest that for that population, about 90% of total vitamin K intakes are provided by K1, about 7.5% by MK-5 through MK-9 and about 2.5% by MK-4
== Cellular and tissue distribution == FPR1 is widely expressed by circulating blood neutrophils, eosinophils, basophils, monocytes, and platelets; tissue-bound macrophages, fibroblasts, and immature dendritic cells; vascular endothelial and smooth muscle cells; various types of epithelial cells, liver hepatocytes, neural tissue glial cells, astrocytes and malignant neuroblastoma cells; skin keratinocytes; and virtually all types of multicellular tissues.
== Relation to humans == Arapaima is exploited in many ways by local human populations. Its tongue is thought to have medicinal qualities in South America. It is dried and combined with guarana bark, which is grated and mixed into water. Doses are given to kill intestinal worms. The bony tongue is used to scrape cylinders of dried guarana, an ingredient in some beverages, and the bony scales are used as nail files. Arapaima produce boneless steaks and are considered a delicacy. In the Amazon region, locals often salt and dry the meat, rolling it into a cigar-style package that is then tied and can be stored without rotting, which is important in a region with little refrigeration. Arapaima are referred to as the "cod of the Amazon", and can be prepared in the same way as traditional salted cod. Designers have begun using the skin of the arapaima as leather to make jackets, shoes, and handbags, and to cover furniture. In July 2009, villagers around Kenyir Lake in Terengganu, Malaysia, reported sighting A. gigas. The "Kenyir monster", or "dragon fish" as the locals call it, was claimed to be responsible for the mysterious drowning of two men on 17 June. In August 2018, India Times reported that arapaima has been spotted in the Chalakudy River, following floods in Kerala; their presence in India is attributed to illegal importation for fish farming. The arapaima is depicted on both the flag and the seal of the Department of Ucayali, Peru.
Sources: en.wikipedia.org
Increased rates of immune system disorders and other wide-ranging symptoms, including chronic pain, fatigue and memory loss, have been reported in over one quarter of combat veterans of the 1991 Gulf War. Combustion products from depleted uranium munitions are being considered as one of the potential causes by the Research Advisory Committee on Gulf War Veterans' Illnesses, as DU was used in 30 mm and 25 mm cannon rounds on a large scale for the first time in the Gulf War. Veterans of the conflicts in the Persian Gulf, Bosnia and Kosovo have been found to have up to 14 times the usual level of chromosome abnormalities in their genes. Serum-soluble genotoxic teratogens produce congenital disorders, and in white blood cells causes immune system damage. A 2005 epidemiology review concluded: "In aggregate the human epidemiological evidence is consistent with increased risk of birth defects in offspring of persons exposed to DU." A 2001 study of 15,000 February 1991 U.S. Gulf War combat veterans and 15,000 control veterans found that the Gulf War veterans were 1.8 (fathers) to 2.8 (mothers) times as likely to have children with birth defects. After examination of children's medical records two years later, the birth defect rate increased by more than 20%:
=== Energy intake === 5-HT2C receptor agonists reduce appetite by working on serotonin receptors in a region of the brain called the hypothalamus. Lorcaserin (Belviq) was FDA approved for weight loss but was withdrawn from the market because a safety clinical trial shows an increased occurrence of cancer. Cannabinoid receptor antagonists were developed to treat obesity because researchers noticed that cannabinoid agonists (such as THC, the main pharmacologically active component of cannabis), increased appetite. However, some drugs in this class such as rimonabant were withdrawn or ceased development due to concerns about mental health and suicide. More selective drugs—some are in development that act only in peripheral tissues, not the brain—may be able to achieve this result with fewer adverse effects. GLP-1 agonists such as tirzepatide, semaglutide, and liraglutide slow gastric emptying and also have neurologically driven effects on appetite. It is unknown if GLP-1 agonists or dual/triple agonists of GLP-1 and/or the glucagon or GIP receptors act solely by reducing energy intake or if they also increase energy expenditure. Setmelanotide is an agonist of the melanocortin 4 receptor and is used in people with certain rare genetic conditions that cause obesity. It is less effective and not approved for general obesity.
This could be due to the branch point at the intermediate α-ketoisovalerate, which can be transaminated to produce valine or further acetylated to generate leucine. There may be different isotope effects associated with the addition of an amino or acetyl group at position C-2 in α-ketoisovalerate. As discussed above, the isotopic consequences of this branch point would depend on the relative rates of leucine vs valine production. One would also expect relative depletion of 13C in leucine because its synthesis requires the addition of another isotopically light acetyl group. In Escherichia coli, the carboxyl carbon in leucine (derived from acetyl-CoA) has a δ13C value roughly 13‰ lower than that of the entire molecule. Curiously, the same depletion is not observed in photoautotrophs. Further, there is little consistency in the δ13C of most amino acids between cyanobacteria and eukaryotic photoautotrophs. These discrepancies demonstrate the limits of our understanding of the mechanisms that set amino acid isotopic compositions. Regardless, isotopic variations between different taxa have been used to great effect in ecology.
Plants usually convert light into chemical energy with a photosynthetic efficiency of 3–6%. Absorbed light that is unconverted is dissipated primarily as heat, with a small fraction (1–2%) reemitted as chlorophyll fluorescence at longer (redder) wavelengths. This fact allows measurement of the light reaction of photosynthesis by using chlorophyll fluorometers. Actual plants' photosynthetic efficiency varies with the frequency of the light being converted, light intensity, temperature, and proportion of carbon dioxide in the atmosphere, and can vary from 0.1% to 8%. By comparison, solar panels convert light into electric energy at an efficiency of approximately 6–20% for mass-produced panels, and above 40% in laboratory devices. Scientists are studying photosynthesis in hopes of developing plants with increased yield. The efficiency of both light and dark reactions can be measured, but the relationship between the two can be complex. For example, the light reaction creates ATP and NADPH energy molecules, which C3 plants can use for carbon fixation or photorespiration. Electrons may also flow to other electron sinks. For this reason, it is not uncommon for authors to differentiate between work done under non-photorespiratory conditions and under photorespiratory conditions. Chlorophyll fluorescence of photosystem II can measure the light reaction, and infrared gas analyzers can measure the dark reaction. An integrated chlorophyll fluorometer and gas exchange system can investigate both light and dark reactions when researchers use the two separate systems together.
Sources: en.wikipedia.org
It consists of a three-amino-acid peptide, glycine-histidine-lysine, bound to one copper(II) ion. The peptide supplies four nitrogen donor atoms, and the resulting complex is stable in neutral aqueous solution. The metal-free peptide is usually called GHK.
The three letters are the standard one-letter codes for glycine, histidine, and lysine. The suffix -Cu indicates the coordinated copper ion. Cosmetic ingredient lists often use the alternative name copper tripeptide-1 for the same complex.
No. Free GHK is the peptide alone, while GHK-Cu contains a bound copper atom. The two differ in colour, charge, and binding behaviour, so any study that measures copper delivery must state which form was used.
GHK-Cu is a complex of the tripeptide glycyl-L-histidyl-L-lysine with copper(II). The peptide binds copper through its histidine residue and neighboring amide nitrogens, forming a stable coordination compound. It is studied as a research chemical and used in some cosmetic formulations.