LL-37 5mg

LL-37 Peptide | Human Antimicrobial Peptide LL-37 | AZOTH

What Is the LL-37 Peptide?

The LL-37 peptide is the only cathelicidin antimicrobial peptide found in humans, and it has become one of the most widely studied antimicrobial peptides in innate immune system research. This human antimicrobial peptide is derived from a precursor protein called hCAP-18, which is cleaved to release the mature peptide LL-37 sequence of 37 amino acids. Human cells, including white blood cells and epithelial cells across barrier tissues, produce this antimicrobial peptide LL-37 as part of the innate immune system’s response to microbial threats. Researchers studying antimicrobial peptides, host defense mechanisms, and infection control have shown consistent interest in the ll 37 peptide because of its dual role in direct antimicrobial activity and immune signaling. At AZOTH, we offer research-grade LL-37 peptide supplied in a hyaluronic acid capsule, synthesized to 99%+ purity, and intended exclusively for researchers and science-focused customers.

Why Is LL-37 Called a Cationic Antimicrobial Peptide?

The peptide ll 37 carries a strong positive charge, which classifies it among the cationic antimicrobial peptides studied for their ability to interact with negatively charged bacterial membranes. This positive charge is central to the molecular basis of how cationic peptides like LL-37 selectively target bacteria over human cells, since bacterial membranes carry a different charge profile than typical mammalian cell membranes. Cationic antimicrobial peptide research consistently points to this electrostatic attraction as the first step in antimicrobial activity, occurring before any membrane disruption takes place. Understanding this mechanism has helped researchers frame LL-37 as a model cationic antimicrobial peptide within the broader cathelicidin family.

The Cathelicidin Family and Where LL-37 Fits

LL-37 belongs to the cathelicidin family of antimicrobial peptides, a group of host defense peptides found across many mammalian species. Unlike other species that produce multiple cathelicidins, humans express only this single antimicrobial peptide, making it the sole human representative of the cathelicidin family and a frequent point of comparison in host defense peptide research. Because of this singular role, antimicrobial peptides researchers often treat LL-37 as a proxy for the entire cathelicidin family when designing in vitro and animal model experiments.

Structure and Precursor Protein Processing

The precursor protein hCAP-18 undergoes proteolytic cleavage by proteinase 3, a serine protease released from neutrophils, to generate the active LL-37 peptide. This precursor protein processing step is tightly regulated, and disruptions in this pathway have been studied for their downstream effects on antimicrobial peptide availability at sites of infection. Research into precursor protein biology continues to refine understanding of how much active peptide is available during acute versus chronic infections.

How Does LL-37 Work? Multiple Mechanisms Explored

The antimicrobial peptide ll 37 does not rely on a single pathway to produce its effects. Preclinical research describes a dual role for LL-37: direct antimicrobial activity against bacteria, fungi, and viruses, paired with immunomodulatory functions that shape immune cell activity. Because of this dual role, antimicrobial peptides like LL-37 are studied both as antimicrobial agents and as immune signaling molecules.

Membrane Disruption and Bacterial Membranes

Research shows that LL-37’s positive charge drives binding to phospholipid membranes and lipopolysaccharides found in the outer membrane of gram negative bacteria. This binding disrupts bacterial membranes and can cause pore formation or full membrane rupture, a mechanism believed to underlie much of the antimicrobial activity documented against pathogens with increased susceptibility to conventional antibiotics. Nature Scientific Reports data describe two distinct interaction pathways for LL-37 within phospholipid membranes, including pore formation in unsaturated bilayers and a separate membrane modulation pathway in more saturated membrane compositions.

Targeting Bacteria Across Gram Positive and Gram Negative Species

LL-37 shows broad spectrum antimicrobial activity against both gram positive bacteria and gram negative bacteria, a property that distinguishes it from many antibiotics that are effective against only one bacterial class. Targeting bacteria across such a wide range of species has made antimicrobial peptide ll 37 a compound of interest for infection control research involving polymicrobial samples. In gram positive bacteria, modifications to the bacterial cell wall, including alterations linked to the dlt operon, have been studied as a mechanism of increased susceptibility or resistance to cationic antimicrobial peptides.

Toll Like Receptors and Innate Immune Signaling

Beyond direct antimicrobial action, research published in J Immunol and J Biol Chem describes how LL-37 interacts with toll like receptors on dendritic cells and other immune cells, modulating pro inflammatory cytokines as part of the innate immune system’s coordinated response. This immunomodulatory function connects the antimicrobial peptide ll 37 to both antimicrobial and inflammation-regulating research categories. Signaling through toll like receptors also links LL-37 research to broader questions about innate immunity and how human cells recognize pathogens through direct contact with bacterial and viral double stranded RNAs.

Dendritic Cells and Pro Inflammatory Cytokines

LL-37 has been shown in J Exp Med studies to influence dendritic cells by altering their maturation and antigen presentation capacity, which in turn shapes downstream T cells activation. This activity connects the antimicrobial peptide to both innate immunity and adaptive immune coordination through dendritic cells and T cells. Pro inflammatory cytokines regulated by LL-37 include several markers studied in the context of anti inflammatory responses during chronic infections.

Biofilm Formation and Chronic Infections

LL-37 has been studied for its capacity to prevent biofilm formation and disrupt existing biofilms in bacteria including Staphylococcus aureus and Pseudomonas aeruginosa, often at concentrations below the minimum inhibitory concentration required for direct bacterial killing. This anti-biofilm activity is a recurring theme in chronic infections research, since biofilm-associated bacteria are notoriously resistant to conventional antibiotics. Research has also compared LL-37’s anti-biofilm activity favorably against certain traditional antibiotics in specific in vitro models, though larger studies are still needed.

Proteolytic Degradation and Peptide Stability

Peptide stability data show LL-37 can resist proteolytic degradation by matrix metalloproteinase-9 in wound fluid, though the peptide remains susceptible to other proteinases such as trypsin. This finding matters for researchers modeling chronic wound environments, since proteolytic degradation directly affects how long an antimicrobial agent like LL-37 remains active at a given site.