LL-37
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Research Use Only
These products are for laboratory research only and not intended for medical use. They are not FDA-approved to diagnose, treat, cure, or prevent any disease. By purchasing, you certify they will be used solely for research and not for human or animal consumption.
Research Summary
24 PubMed CitationsOverview LL-37 is a 37-residue cationic antimicrobial peptide (AMP) and the only member of the cathelicidin family identified in humans. Its amino acid sequence is LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES.[1] Parent molecule: LL-37 is derived from a larger, inactive precursor protein called hCAP18 (human Cationic Antimicrobial Protein, 18 kDa). The CAMP gene on chromosome 3p21.3 encodes hCAP18. The active LL-37 peptide is released extracellularly through proteolytic cleavage — primarily by proteinase 3 in neutrophils and kallikreins (K5/K7) in keratinocytes.[2] Cellular origin: Constitutively expressed or induced in neutrophils (stored in specific granules), monocytes, mast cells, and epithelial cells of the skin, gastrointestinal tract, and respiratory tract.[3] Structurally, LL-37 is a linear, amphipathic peptide (MW 4493.33 Da) with a net charge of +6 at physiological pH. It is cysteine-free and adopts an α-helical structure in membrane environments but remains disordered in aqueous solution. NMR studies reveal a curved helix-bend-helix motif spanning residues 2–31 with a disordered...
LL-37 — Research Data at a Glance
| Property | Value |
|---|---|
| PubMed Citations Referenced | 24 |
| Contributing Researchers | 3 |
| Storage Conditions | Lyophilized powder/concentrate stored at -20°C. |
| Purity Standard | ≥99% (HPLC verified, 3rd-party COA) |
| Research Use Only | Not for human consumption. RUO only. |
Overview
Overview
LL-37 is a 37-residue cationic antimicrobial peptide (AMP) and the only member of the cathelicidin family identified in humans. Its amino acid sequence is LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES.[1]
Parent molecule: LL-37 is derived from a larger, inactive precursor protein called hCAP18 (human Cationic Antimicrobial Protein, 18 kDa). The CAMP gene on chromosome 3p21.3 encodes hCAP18. The active LL-37 peptide is released extracellularly through proteolytic cleavage — primarily by proteinase 3 in neutrophils and kallikreins (K5/K7) in keratinocytes.[2]
Cellular origin: Constitutively expressed or induced in neutrophils (stored in specific granules), monocytes, mast cells, and epithelial cells of the skin, gastrointestinal tract, and respiratory tract.[3]
Structurally, LL-37 is a linear, amphipathic peptide (MW 4493.33 Da) with a net charge of +6 at physiological pH. It is cysteine-free and adopts an α-helical structure in membrane environments but remains disordered in aqueous solution. NMR studies reveal a curved helix-bend-helix motif spanning residues 2–31 with a disordered C-terminal tail.[1]
LL-37 expression in the skin is regulated by Vitamin D. Abnormal LL-37 levels are linked to psoriasis (overexpression) and atopic dermatitis (suppression).[6]
Mechanism of Action
Mechanism of Action
Primary Antimicrobial: "Carpet-Like" Membrane Disruption
LL-37 disrupts bacterial membranes via electrostatic attraction to anionic bacterial surfaces → hydrophobic insertion → toroidal pore formation or micellization ("carpet-like" mechanism). It acts preferentially on Gram-negative bacteria but is effective against both Gram-positive and drug-resistant strains. Eukaryotic membranes are protected by high cholesterol content.[3][7]
Receptor Targets
| Receptor | Type | Functional Effect |
|---|---|---|
| FPR2/FPRL1 | GPCR | Chemotaxis of neutrophils, monocytes, T cells (Yang et al., 2000)[8] |
| P2X7 | Purinergic | IL-1β processing; neutrophil survival (Elssner et al., 2004)[8] |
| EGFR | Receptor Tyrosine Kinase | Transactivation → keratinocyte migration → wound healing (Tokumaru et al., 2005)[9] |
| IGF-1R | Receptor Tyrosine Kinase | Partial agonist → proliferation (Girnita et al., 2012)[10] |
| CXCR2 | Chemokine | Functional ligand on neutrophils (Zhang et al., 2009)[8] |
| MrgX2 | GPCR | Mast cell degranulation (Subramanian et al., 2011)[8] |
| TLR9 | Toll-like Receptor | DNA-LL-37 complexes trigger endosomal TLR9 (Lande et al., 2007)[10] |
Downstream Signaling Cascades
- ERK1/2 and p38 MAPK: Crucial for keratinocyte migration and wound healing; modulates cytokine production in monocytes.[9]
- PI3K/Akt → CREB: Cell survival signaling via P2X7–SFK–Akt pathway in keratinocytes.[9]
- mTOR: Activation suppresses autophagy in pancreatic cancer → ROS accumulation → DNA damage.[11]
- NF-κB: Inhibits p50/p65 translocation in inflammation (anti-inflammatory); may activate in some cancers (context-dependent).[8]
Anti-Biofilm Activity
Inhibits quorum-sensing (Las/Rhl systems) and promotes twitching motility; effective at sub-MIC concentrations (0.5 µg/mL) — far below bactericidal thresholds.[7]
LPS Neutralization
Binds and neutralizes lipopolysaccharide (LPS), preventing endotoxin-induced macrophage activation and cytokine storm.[12]
Biphasic Dose-Response
LL-37 exhibits a distinct bell-shaped dose response: ≤1 µM = anti-apoptotic, pro-healing; >10 µM = cytotoxic. In clinical trials, 0.5 mg/mL was 6-fold more effective than placebo, while the highest dose (3.2 mg/mL) showed no improvement.[5]
vs. Related Compounds
| Compound | Key Difference |
|---|---|
| hCAP18 | Inactive 18 kDa precursor; LL-37 is the active C-terminal domain released by proteolysis |
| KR-12 | Truncated fragment (residues 18–29); retains antimicrobial activity with less cytotoxicity |
| D-LL-37 | Protease-resistant enantiomer; retains antimicrobial and anti-biofilm activity |
| CRAMP (mouse) | Murine ortholog; functional homology but non-identical sequence |
Research Applications
Research Applications
LL-37 research spans antimicrobial resistance, wound healing, oncology, and immunology across 8+ indication categories:
- Chronic Wound Healing — Promotes granulation tissue, re-epithelialization, and angiogenesis in venous leg ulcers (VLUs) and diabetic foot ulcers (DFUs).[5][13]
- Antimicrobial Resistance — Broad-spectrum activity against MDR bacteria; anti-biofilm; synergy with conventional antibiotics (azithromycin, colistin, ciprofloxacin, vancomycin).[7]
- Oncology (Dual Role) — Anti-tumorigenic: colon, gastric, and pancreatic cancer (apoptosis, autophagy suppression, immune reprogramming). Pro-tumorigenic: breast, lung, ovarian, and melanoma (context-dependent).[11][10]
- Antiviral Research — RSV, Influenza A, HSV-1, HIV-1 — disrupts viral envelopes and blocks entry.[3]
- Antifungal Research — Active against Candida albicans and Cryptococcus neoformans via membrane permeabilization.[3]
- Sepsis/Endotoxemia — LPS neutralization prevents endotoxin-induced macrophage activation and cytokine storms.[12]
- Bone Regeneration — Stimulates proliferation and osteogenic differentiation of BMSCs; recruits MSCs to injury sites.[14]
- Drug Delivery Systems — Lipid nanoparticles, chitosan nanoparticles, hydrogels for improved stability and reduced cytotoxicity.[15]
Biochemical Characteristics
| Property | Value |
|---|---|
| Molecular Formula | C₂₀₅H₃₄₀N₆₀O₅₃ |
| Molecular Weight | 4493.33 Da |
| CAS Number | Not established |
| PubChem CID | 16198951 |
| Sequence (1-Letter) | LLGDFFRKSKEKIGKEFKRIVQRIKDFLRNLVPRTES |
| Sequence (3-Letter) | Leu-Leu-Gly-Asp-Phe-Phe-Arg-Lys-Ser-Lys-Glu-Lys-Ile-Gly-Lys-Glu-Phe-Lys-Arg-Ile-Val-Gln-Arg-Ile-Lys-Asp-Phe-Leu-Arg-Asn-Leu-Val-Pro-Arg-Thr-Glu-Ser |
| Structure | Linear, amphipathic α-helix (in membranes), cysteine-free, curved helix-bend-helix motif (residues 2–31) |
| Net Charge | +6 at physiological pH |
| Gene Origin | CAMP gene, chromosome 3p21.3 — encodes hCAP18 precursor |
| Classification | Cathelicidin Antimicrobial Peptide / Host Defense Peptide |
| Clinical Name | Ropocamptide (Promore Pharma AB) |
Identifiers
| Purity Standard | |
|---|---|
| Identity Confirmation | |
| Counter-Ion | |
| Detection Methods |
Preclinical Research Summary
Preclinical Research Summary
Key Preclinical Studies
| Study | Model | Key Findings | Ref |
|---|---|---|---|
| Zhang et al. (2022) | C57/BL6 mice, Pan02 PDAC — 20 mg/kg/day IP × 14d | 42% reduction in tumor growth (p<0.05); ↓ MDSCs and M2 macrophages (p<0.01); ↑ CD4+/CD8+ T cells (p<0.01); fewer AEs vs gemcitabine | [11] |
| Overhage et al. (2008) | P. aeruginosa biofilm — 0.5 µg/mL | Inhibits biofilm formation via quorum-sensing downregulation (Las/Rhl); promotes twitching motility at sub-MIC | [7] |
| Wu et al. (2010) | Colon cancer cells | LL-37 inhibits proteasome → activates BMP signaling → p21Waf1 → cell cycle arrest | [10] |
| Koczulla et al. (2003) | Dexamethasone-treated mice — topical LL-37 | Increased vascularization and re-epithelialization; key role in wound regeneration via angiogenesis | [9] |
| Beaumont et al. (2014) | Bone marrow stromal cells | Stimulates proliferation and osteogenic differentiation of BMSCs; recruits MSCs to injury sites | [14] |
| Tuberculosis (in vivo) | M. tuberculosis mice — ~1 mg/kg IT 3x/wk × 28d | 3–10 fold reduction in lung bacilli; effective against drug-sensitive and MDR strains | [7] |
Clinical Trials
| Trial | Population | Intervention | Key Results | Ref |
|---|---|---|---|---|
| Phase IIb VLU | n=148 | Topical 0.5 mg/mL, 3x/wk × 13 wk | Total population: NS. Subgroup (ulcers ≥10 cm²): 28.1% vs 8.1% closure (p=0.0458); healing rate 0.0367/day vs 0.0093/day (p=0.0439) | [16] |
| Phase I/II VLU | n=34 | Topical 0.5/1.6/3.2 mg/mL, 2x/wk × 4 wk | 0.5 mg/mL healing rate 6-fold higher than placebo (p=0.003); ulcer area ↓ 68%; bell-shaped dose-response | [5] |
| RCT — DFU | n=25 | LL-37 cream 0.5 mg/g, 2x/wk × 4 wk | Granulation index significantly ↑ days 7–28 (p<0.05); 11/13 vs 3/12 achieved >0.41 increase; no effect on bacterial load | [13] |
| Phase I Melanoma | n=36 planned | Intratumoral 250–2000 µg/tumor, weekly × 8 wk | Acceptable tolerability; variable biological response; dermatologic toxicity noted | [17] |
Safety Summary
| Parameter | Finding |
|---|---|
| Clinical | Safe and well-tolerated in 148-patient Phase IIb; no systemic safety concerns; mild local reactions (redness, edema) |
| Dose-Dependent | 3.2 mg/mL → increased local reactions; bell-shaped dose-response |
| Cytotoxicity | >13–25 µM towards eukaryotic cells; significantly inhibited by serum |
| Cancer Risk | Context-dependent: anti-tumorigenic in colon/gastric/pancreatic; pro-tumorigenic in breast/lung/ovarian/melanoma |
| Drug Interactions | Synergy with antibiotics (azithromycin, colistin, vancomycin); inhibited by glycosaminoglycans; Vitamin D upregulates expression |
| Stability | Susceptible to protease degradation; short plasma half-life; D-LL-37 enantiomer is protease-resistant |
The products offered on this website are furnished for in-vitro studies only. In-vitro studies (Latin: in glass) are performed outside of the body. These products are not medicines or drugs and have not been approved by the FDA to prevent, treat or cure any medical condition, ailment or disease. Bodily introduction of any kind into humans or animals is strictly forbidden by law.
For Laboratory Research Only. Not for human use, medical use, diagnostic use, or veterinary use.
ALL ARTICLES AND PRODUCT INFORMATION PROVIDED ON THIS WEBSITE ARE FOR INFORMATIONAL AND EDUCATIONAL PURPOSES ONLY.
Authors & Attribution
✍️ Article Author
Dr. Gudmundur Hrafn Gudmundsson
Gudmundur Hrafn Gudmundsson is a Professor at the University of Iceland and Karolinska Institutet (Sweden). He played a foundational role in the discovery of LL-37, cloning the FALL-39 gene and isolating the mature peptide from human neutrophils. His work established the processing mechanism of the precursor protein hCAP18 into the active antimicrobial peptide LL-37. Key publications: 'FALL-39, a putative human peptide antibiotic, is cysteine-free and expressed in bone marrow and testis' (1995), 'The human gene FALL39 and processing of the cathelin precursor to the antibacterial peptide LL-37 in granulocytes' (1996), and 'Conformation-dependent antibacterial activity of the naturally occurring human peptide LL-37' (1998). Gudmundur Hrafn Gudmundsson is referenced as a foundational scientist in LL-37 research. In no way is this doctor/scientist endorsing or advocating the purchase, sale, or use of this product for any reason. There is no affiliation or relationship, implied or otherwise, between Pure US Peptide and this doctor.
View Full Researcher Profile →🎓 Scientific Journal Author
Dr. Birgitta Agerberth, PhD
Birgitta Agerberth, PhD, is a key researcher at Karolinska Institutet (Sweden) who was instrumental in the original isolation and biochemical characterization of LL-37. Her research focuses on the peptide's conformation, antibacterial activity, and expression in different tissues and immune cells. She also investigated LL-37's role in diseases such as cystic fibrosis and its presence in biofluids. Key publications: 'FALL-39, a putative human peptide antibiotic' (1995), 'Conformation-dependent antibacterial activity of the naturally occurring human peptide LL-37' (1998), and 'The human antimicrobial and chemotactic peptides LL-37 and alpha-defensins are expressed by specific lymphocyte and monocyte populations' (2000). Birgitta Agerberth is referenced as a key scientist in LL-37 research. In no way is this doctor/scientist endorsing or advocating the purchase, sale, or use of this product for any reason. There is no affiliation or relationship, implied or otherwise, between Pure US Peptide and this doctor.
View Full Researcher Profile →Dr. Birgitta Agerberth, PhD is being referenced as one of the leading scientists involved in the research and development of LL-37. In no way is this doctor/scientist endorsing or advocating the purchase, sale, or use of this product for any reason. There is no affiliation or relationship, implied or otherwise, between Pure US Peptide and this doctor. The purpose of citing the doctor is to acknowledge, recognize, and credit the exhaustive research and development efforts conducted by the scientists studying this peptide.
🔬 Contributing Researcher
Dr. Richard L. Gallo, MD, PhD
Richard L. Gallo, MD, PhD, is a Professor at the University of California, San Diego, Division of Dermatology. His research has been pivotal in defining LL-37's role in skin innate immunity and dermatological diseases. He demonstrated that LL-37 expression in the skin is induced by injury and is critical for defense against infections like Group A Streptococcus. His work linked abnormal LL-37 levels to psoriasis (overexpression) and atopic dermatitis (suppression), and established the regulation of LL-37 by Vitamin D. Key publications: 'Innate antimicrobial peptide protects the skin from invasive bacterial infection' (2001), 'Cathelicidin antimicrobial peptides block dendritic cell TLR4 activation and allergic contact sensitization' (2007). Richard L. Gallo is referenced as a leading scientist in LL-37 research. In no way is this doctor/scientist endorsing or advocating the purchase, sale, or use of this product for any reason. There is no affiliation or relationship, implied or otherwise, between Pure US Peptide and this doctor.
View Full Researcher Profile →Dr. Richard L. Gallo, MD, PhD is being referenced as one of the leading scientists involved in the research and development of LL-37. In no way is this doctor/scientist endorsing or advocating the purchase, sale, or use of this product for any reason. There is no affiliation or relationship, implied or otherwise, between Pure US Peptide and this doctor. The purpose of citing the doctor is to acknowledge, recognize, and credit the exhaustive research and development efforts conducted by the scientists studying this peptide.
Referenced Citations
Johansson J, Gudmundsson GH, Rottenberg ME, et al. Conformation-dependent antibacterial activity of the naturally occurring human peptide LL-37. Journal of Biological Chemistry. 1998;273(6):3718-3724.
PubMedGudmundsson GH, Agerberth B, Odeberg J, et al. The human gene FALL39 and processing of the cathelin precursor to the antibacterial peptide LL-37 in granulocytes. European Journal of Biochemistry. 1996;238(2):325-332.
PubMedRidyard KE, Overhage J. The Potential of Human Peptide LL-37 as an Antimicrobial and Anti-Biofilm Agent. Antibiotics. 2021;10(6):650.
DOIDuplantier AJ, van Hoek ML. The Human Cathelicidin Antimicrobial Peptide LL-37 as a Potential Treatment for Polymicrobial Infected Wounds. Frontiers in Immunology. 2013;4:143.
DOIGrönberg A, Mahlapuu M, Ståhle M, et al. Treatment with LL-37 is Safe and Effective in Enhancing Healing of Hard-to-Heal Venous Leg Ulcers: A Randomized, Placebo-Controlled Clinical Trial. Wound Repair and Regeneration. 2014;22(5):613-621.
DOIYang B, Good D, Mosaiab T, et al. Significance of LL-37 on Immunomodulation and Disease Outcome. BioMed Research International. 2020;2020:8349712.
DOIHeilborn JD, Nilsson MF, Kratz G, et al. The cathelicidin anti-microbial peptide LL-37 is involved in re-epithelialization of human skin wounds and is lacking in chronic ulcer epithelium. Journal of Investigative Dermatology. 2003;120(3):379-389.
DOIScott MG, Davidson DJ, Gold MR, et al. The human antimicrobial peptide LL-37 is a multifunctional modulator of innate immune responses. The Journal of Immunology. 2002;169(7):3883-3891.
DOISvensson D, Nilsson BO. Human antimicrobial/host defense peptide LL-37 may prevent the spread of a local infection through multiple mechanisms: an update. Inflammation Research. 2025;74(1):36.
DOIPiktel E, Niemirowicz K, Wnorowska U, et al. The Role of Cathelicidin LL-37 in Cancer Development. Archivum Immunologiae et Therapiae Experimentalis. 2016;64(1):33-46.
DOIZhang Z, Chen WQ, Zhang SQ, et al. The human cathelicidin peptide LL-37 inhibits pancreatic cancer growth by suppressing autophagy and reprogramming of the tumor immune microenvironment. Frontiers in Pharmacology. 2022;13:906625.
DOILu F, Zhu Y, Zhang G, Liu Z. Renovation as innovation: Repurposing human antibacterial peptide LL-37 for cancer therapy. Frontiers in Pharmacology. 2022;13:944147.
DOIMiranda E, Bramono K, Yunir E, et al. Efficacy of LL-37 cream in enhancing healing of diabetic foot ulcer: a randomized double-blind controlled trial. Archives of Dermatological Research. 2023;315(9):2623-2633.
DOISeil M, Nagant C, Dehaye JP, et al. Spotlight on Human LL-37, an Immunomodulatory Peptide with Promising Cell-Penetrating Properties. Pharmaceuticals. 2010;3(11):3435-3460.
DOIErgün FC, Kars MD, Kars G. Development and Characterization of LL37 Antimicrobial-Peptide-Loaded Chitosan Nanoparticles. Polymers. 2025;17(13):1884.
DOIMahlapuu M, Sidorowicz A, Mikosinski J, et al. Evaluation of LL-37 in healing of hard-to-heal venous leg ulcers: A multicentric prospective randomized placebo-controlled clinical trial. Wound Repair and Regeneration. 2021;29(6):938-950.
DOIOhuchi K, Ikawa T, Amagai R, et al. LL-37 Might Promote Local Invasion of Melanoma by Activating Melanoma Cells and Tumor-Associated Macrophages. Cancers. 2023;15(6):1678.
DOIMiura S, Garcet S, Li X, et al. Cathelicidin Antimicrobial Peptide LL37 Induces Toll-Like Receptor 8 and Amplifies IL-36γ and IL-17C in Human Keratinocytes. Journal of Investigative Dermatology. 2023;143(5):832-841.e4.
DOILin X, Wang R, Mai S. Advances in delivery systems for the therapeutic application of LL37. Journal of Drug Delivery Science and Technology. 2020;60(9):102016.
DOIWu WK, Wang G, Coffelt SB, et al. Emerging Roles of the Host Defense Peptide LL-37 in Human Cancer and its Potential Therapeutic Applications. International Journal of Cancer. 2010;127(8):1741-1747.
DOIAlalwani SM, Sierigk J, Herr C, et al. The antimicrobial peptide LL-37 modulates the inflammatory and host defense response of human neutrophils. European Journal of Immunology. 2010;40(4):1118-1126.
DOILozeau LD, Kole D, Dominko T, et al. Activity and toxicity of a recombinant LL37 antimicrobial peptide. Frontiers in Bioengineering and Biotechnology. 2016.
DOIWan W, Zhang L, Lin Y, et al. Mitochondria-derived peptide MOTS-c: effects and mechanisms related to stress, metabolism and aging. Journal of Translational Medicine. 2023;21(1):36.
DOIM.D. Anderson Cancer Center. Induction of Antitumor Response in Melanoma Patients Using the Antimicrobial Peptide LL37. ClinicalTrials.gov Protocol NCT02225366. 2015.
SourceRUO Disclaimer
For Research Use Only (RUO). This product is intended solely for in-vitro research and laboratory experimentation. It is not a drug, food, cosmetic, or medical device and has not been approved by the FDA for any human or veterinary use. It must not be used for therapeutic, diagnostic, or any other non-research purpose. Pure US Peptide does not condone or encourage the use of this product for anything other than strictly defined research applications. Users assume full responsibility for compliance with all applicable regulations and guidelines.
Certificate of Analysis (COA)
Every batch is strictly tested by accredited third-party laboratories (ISO 17025) to ensure 99%+ purity.
Latest Lab Report
Storage & Handling
Summary
Lyophilized powder/concentrate stored at -20°C. Cream formulation stable >99 months at 4°C, >75 months at 28°C (melts at 40°C). Reconstituted solutions should be used immediately or frozen.
Recommended Laboratory Storage Conditions
Lyophilized Powder/Concentrate: Store frozen at -20°C. Stable for extended periods in lyophilized form.
Cream Formulation: Clinical-grade LL-37 cream maintains >90% active ingredient for up to 99 months at 4°C and 75 months at 28°C. Cream melts at 40°C — store below this threshold.
Reconstitution: Use sterile diluent (polyvinyl alcohol or bacteriostatic water). Use immediately or keep frozen to prevent degradation and aggregation.
Form: Synthetic peptide acetate salt via solid-phase peptide synthesis (SPPS); lyophilized sterile powder.
Purity: ≥90–110% content by HPLC (UV at 217 nm); identity confirmed by LC-MS.
Handling: Allow vials to warm to room temperature before opening to prevent moisture condensation.
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