American Society of Hirudotherapy

Theromacin

Antimicrobial peptide active against Gram-negative bacteria — innate immunity of leech.

Preclinical / mechanisticLast updated: 2026-05-26 · Reviewed by ASH Editorial Board
Molecular weight of Theromacin compared with other characterized leech-derived compoundsHementerin80 kDaHementin80 kDaHementin-Like Protein (HLP-1)80 kDaLeech Collagenase70 kDaHaemadipsa yanyuanensis Progr…70 kDaLeech Apyrase67 kDaCalin65 kDaHyaluronidase60 kDaAntithrombin III binding prot…58 kDaCollagenolytic Fibrinolysin55 kDaLeech Thrombospondin-Like Pro…50 kDaTheromacin4.7 kDa
Molecular weight (kilodaltons) of Theromacin (highlighted) alongside other characterized leech salivary compounds. Smaller proteins/peptides generally diffuse and act faster.

Mechanistic Evidence Box

Preclinical / mechanistic
Page type
Compound profile
Evidence type
Antimicrobial peptide active against Gram-negative bacteria — innate immunity of leech.
Evidence level
In vitro
Drug vs leech
Purified natural compound

Clinical translation limit

Theromacin's in vitro antimicrobial activity does not establish clinical efficacy as a therapeutic antibiotic. No FDA-approved derivative exists. Mechanism is preclinical/biochemical only.

Molecular Profile

Category
Antimicrobial
Evidence tier
Preclinical
Molecular weight
4,700 Da
Source species
Theromyzon tessulatum
Discovered
2004 · Tasiemski et al.
Theromacin molecular structure

Biological Targets

  • → Gram-negative bacterial membranes

Key Citations

  1. Tasiemski A et al. (2004), J Biol Chem

External Resources

    Related Antimicrobial Compounds

    Theromyzin

    Antimicrobial peptide; structural analogue of mammalian defensin family.

    Macrostomin

    Antimicrobial peptide active against Gram-positive bacteria — amphipathic alpha-helix.

    Hirunipins

    Newly-characterized antimicrobial peptide family (Kumar 2025) — candidate next-generation antibiotics against AMR pathogens.

    Destabilase Lysozyme Activity

    Lysozyme domain of destabilase — antimicrobial activity against peptidoglycan-containing bacteria.

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    This website provides educational information and does not constitute medical advice, diagnosis, or treatment recommendations. Medicinal leech therapy carries clinically meaningful risks and should be performed only by qualified clinicians under institutionally approved protocols. FDA 510(k) clearance for medicinal leeches is limited to specific indications; investigational and off-label discussions are labeled accordingly. For patient-specific guidance, consult a qualified healthcare provider.