Indolicidin is a short peptide with antibacterial activity, belonging to a type of natural antimicrobial peptide. Composed of 13 amino acid residues, these amino acids are linked together through peptide bonds to form a compact peptide chain. In solution, it presents a helical conformation that facilitates its interaction with other molecules or cellular structures. Due to its specific amino acid composition and sequence, it can selectively bind to targets in organisms, thereby exerting its antibacterial activity.
Under appropriate conditions, it can maintain the stability of its structure and activity. However, at higher temperatures, its peptide bonds may be disrupted, leading to structural changes and loss of activity. Therefore, in research and application, it is necessary to control the experimental temperature to ensure its stability and activity. As a natural antimicrobial peptide, it has various functions such as antibacterial, immune regulation, anti-tumor, and antiviral.
Customized Bottle Caps & Corks
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Indolicidin COA
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Chemical Formula |
C100H132N26O13 |
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Exact Mass |
1905 |
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Molecular Weight |
1906 |
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m/z |
1906 (100.0%), 1905 (92.5%), 1907 (39.5%), 1907 (14.0%), 1908 (10.8%), 1907 (9.6%), 1906 (8.9%), 1908 (7.2%), 1909 (4.3%), 1908 (3.8%), 1908 (2.7%), 1907 (2.5%), 1907 (1.5%), 1909 (1.4%), 1906 (1.4%), 1908 (1.3%), 1909 (1.0%) |
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Elemental Analysis |
C, 63.01; H, 6.98; N, 19.10; O, 10.91 |
antibacterial activity
Indolicidin exhibits broad-spectrum antibacterial activity against a wide range of microorganisms, including various aerobic Gram-negative bacteria, Gram-positive bacteria, and fungi. This broad spectrum of activity makes it a promising candidate for antimicrobial therapy.
Membrane Permeabilization
The unique chemical structure, rich in tryptophan residues and with an amidated carboxyl terminus, allows it to penetrate bacterial cell membranes and disrupt their integrity. This leads to the efflux of bacterial contents, ultimately resulting in bacterial death.
DNA Binding and Inhibition of Replication
Studies have shown that it can bind to double-helical DNA, possibly inhibiting a large number of enzymes related to DNA processing. Specifically, the PW-WP structural motif in the middle of the thirteen-peptide is a special structural element that can envelop the B-form DNA double helix, enhancing its stability and inhibiting DNA replication and transcription.
In vitro experiments have demonstrated its high bactericidal ability, with near-complete killing of common pathogenic strains such as Escherichia coli and Staphylococcus aureus. This efficacy highlights its potential as an antimicrobial agent.
Limitations & Derivative Development
Despite its significant antibacterial activity, the clinical application is limited due to its cytotoxicity to red blood cells, which can easily cause hemolysis.
Additionally, its high affinity for binding to surface lipopolysaccharides, while contributing to its antibacterial effect, may also lead to the development of drug resistance in certain pathogens.
To overcome these limitations, researchers have developed various derivatives and analogs.
For example, Indolicidin acetate and Indolicidin TFA are derivatives obtained through chemical modification that maintain antibacterial activity while reducing toxicity to red blood cells.Furthermore, some studies have attempted to enhance the antibacterial spectrum and reduce cytotoxicity by altering the amino acid sequence, such as X-indolicidin, which is formed by oxidizing two indole ring side chains and retains the same amino acid sequence and antibacterial activity while being resistant to proteases.
Antiviral Effects
Indolicidin also demonstrates antiviral properties, particularly against certain viruses such as HIV-1 and herpes simplex virus. Its antiviral mechanism is somewhat different from its antifungal action. Studies have shown that it can directly bind to DNA, interfering with the formation of integrase-DNA complexes rather than binding to the integrase itself. This binding may inhibit a range of enzymes associated with DNA processing, thus inhibiting viral replication.
HIV-1 Inhibition
It has been found to inhibit HIV-1 replication effectively. The antiviral concentration required is higher than that for antibacterial and antifungal activities.
For instance, a concentration of 333 ug/ml can inhibit HIV-1, with an IC50 value ranging from 67 to 100 ug/ml at 37°C. Exposure to it for 5 minutes at 37°C can inhibit 50% of HIV virus replication, while complete antiviral activity requires approximately 60 minutes.
Mechanism of Action
Research suggests that it binds to DNA, specifically the PW-WP structural domain within the indolicidin thirteen-peptide, which can wrap around the B-form DNA double helix, enhancing its stability and inhibiting DNA replication and transcription. This binding ability is crucial for its antiviral activity.
Immunomodulatory Effects
Indolicidin has been shown to augment the immune system's reaction, helping the body better resist infections and diseases. This is attributed to its ability to interact with immune cells and stimulate them to mount a stronger defense.
Cytokines are signaling molecules that play a pivotal role in immune regulation. It can influence the production of cytokines, such as interleukins and chemokines, which are involved in orchestrating immune responses.
Innate immune cells, such as neutrophils, macrophages, and natural killer (NK) cells, are the first line of defense against infections. It can enhance the activity of these cells, making them more effective at killing pathogens or targeting abnormal cells.
Although the direct effects on adaptive immunity (T and B cell responses) have not been extensively studied, its ability to modulate innate immune responses may indirectly influence adaptive immune responses.
In addition to its direct antimicrobial activity, it also exhibits anti-inflammatory properties. This is important in preventing excessive inflammation, which can be damaging to tissues and organs. By regulating inflammatory pathways, it contributes to maintaining immune homeostasis.
Final Solution
Therapy in Infectious Diseases
By enhancing the immune response, it could be used as an adjuvant therapy to improve the efficacy of antibiotics or vaccines.
Treatment of Autoimmune Diseases
By modulating immune responses, it might be useful in the treatment of autoimmune diseases.
Cancer Therapy
Although direct antitumor effects have not been conclusively demonstrated, its immunomodulatory properties could be harnessed.
Indolicidin is a natural antimicrobial peptide (AMP) composed of 13 amino acids, originally isolated from bovine neutrophils. Its unique tryptophan (Trp) and proline (Pro) structure endows it with broad-spectrum antibacterial, antiviral and antifungal activities, as well as inhibitory effects on some cancer cells. Due to its potential clinical application value, the synthesis and production of Indolicidin have become a research hotspot. This article will elaborate on the manufacturing information from four aspects: chemical synthesis, recombinant express, modification optimization, and challenges in large-scale production.
Chemical Synthesis Method
Chemical synthesis is the main method for large-scale production of Indolicidin in the laboratory, and it is particularly suitable for structural modification studies.
Solid Phase Peptide Synthesis (SPPS)
Principle: Based on the Fmoc (fluorene methoxycarbonyl) or Boc (tert-butoxycarbonyl) protection strategies, peptide chains are gradually assembled on the resin.
Steps:
Resin selection: Commonly used resins are Rink amide resin or Wang resin.
Amino acid coupling: 13 amino acids are connected in sequence (sequence: ILPWKWPWWPWRR-NH₂), and tryptophan (W) requires special protection (such as Boc-Trp(Boc)-OH).
Cutting and purification: The peptide chains are cut using trifluoroacetic acid (TFA), and then purified by high-performance liquid chromatography (HPLC) (the purity is usually > 95%).
Advantages: High flexibility, allowing the introduction of non-natural amino acids or modifying groups.
Disadvantage: High cost, not suitable for large-scale production.
Liquid-phase Synthesis
This method is suitable for the connection of short peptide fragments, but it is less commonly used for the synthesis of Indolicidin.
Recombinant Express Method
To reduce costs and achieve large-scale production, researchers have attempted to express Indolicidin through microbial or cellular systems recombination.
Prokaryotic Express System
Host bacteria: Escherichia coli (E. coli) is the most commonly used host, but the following issues need to be addressed:
Toxicity: Indolicidin has a killing effect on host cells. The express timing needs to be strictly controlled using inducible promoters (such as T7 or araBAD).Solubility: Prone to form inclusion bodies. Fusion tags (such as SUMO, Trx) are required to enhance solubility. The target peptide can be released through enzymatic cleavage subsequently.Process Optimization:Express at low temperature (20-25°C) leads to a reduction in the formation of inclusion bodies.The secretion signal peptide (such as PelB) is used to secrete the peptide into the periplasmic space, thereby reducing intracellular toxicity.
Eukaryotic Express System
Yeast system (such as Pichia pastoris):
Advantage: Capable of post-translational modification, suitable for complex peptides.
Challenge: Indolicidin may be degraded by yeast proteases, so a protease-deficient strain needs to be used.
Mammalian cells: Excessively costly, intended solely for research purposes.
Downstream Processing
Cell disruption and capture: Cells are disrupted using ultrasound or high-pressure homogenization, and the fusion protein is purified through affinity chromatography.
Enzymatic cleavage and purification: Use enterokinase or SUMO protease to remove the tags, and then perform reversed-phase HPLC purification of the target peptides.
Structural modification and optimization
The natural Indolicidin exhibits hemolytic toxicity and proteinase instability, and thus requires modification to improve its performance.
Amino acid substitution
Reduce toxicity: Replace Arg (R) with hydrophobic amino acids (such as Ala), reducing the interaction with mammalian cell membranes.
Enhance stability: Introduce D-type amino acids or β-amino acid resistance proteins to resist protease degradation.
Lipidation/PEGylation
N-terminal acetylation or attachment of polyethylene glycol (PEG) prolongs the half-life.
Heterodipeptide Design
Fusion with other AMP fragments (such as LL-37) to enhance activity or broaden the antibacterial spectrum.
Challenges of Large-scale Production
Cost Control
Chemical synthesis: The cost per gram can reach several thousand dollars, which is not suitable for clinical needs.Reorganization of express: The fermentation process needs to be optimized (such as through high-density cultivation) to increase production.
Quality Control
Purity requirements: The medicinal peptides must comply with the FDA/EMA standards (impurities < 0.1%).Activity assay: The minimum inhibitory concentration (MIC) and hemolysis test (HC₅₀) are the key indicators.
Regulations and Safety
It is necessary to conduct preclinical toxicological evaluations, especially for immunogenicity and long-term toxicity.
Future Outlook
Cell-free synthesis: Producing rapidly using an in vitro translation system, avoiding host toxicity.Nanocarrier delivery: Enhancing targeting by combining liposomes or polymers.
AI-assisted design: Predicting efficient and low-toxic variants through machine learning.
The production of indolicidin requires a balance between the precision of chemical synthesis and the scalability of recombinant express and nanotechnology), its clinical application is expected to be promoted.
FAQ
Indolcidin is a kind of natural active antimicrobial peptide with excellent broad-spectrum antibacterial activity. It can effectively inhibit and eliminate various gram-positive bacteria, gram-negative bacteria and partial fungi, and also possess certain anti-inflammatory effects. It can suppress the release of inflammatory factors, relieve local inflammatory lesions, and maintain stable physiological state of organisms.
It has rich application value in multiple industries. It can be used as high-efficiency antibacterial raw material for animal feeding additives to reduce livestock and poultry infection rate. Besides, it can also be applied in daily chemical antisepsis, biomedical research and skin external care products, playing a safe and stable antibacterial and protective role.
Different from traditional chemical bacteriostatic agents, Indolcidin features low drug resistance risk and good biocompatibility. It acts rapidly on pathogenic microorganisms with mild efficacy, will not easily damage normal tissue cells, and owns good thermal stability and acid-base tolerance, which is convenient for formula processing and long-term storage in various preparations.
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