American Society of Hirudotherapy

Theromyzin

Antimicrobial peptide; structural analogue of mammalian defensin family.

Preclinical / mechanisticLast updated: 2026-05-26 · Reviewed by ASH Editorial Board
Molecular weight of Theromyzin 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 kDaTheromyzin4.3 kDa
Molecular weight (kilodaltons) of Theromyzin (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; structural analogue of mammalian defensin family.
Evidence level
In vitro
Drug vs leech
Purified natural compound

Clinical translation limit

Theromyzin'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
4,300 Da
Source species
Theromyzon tessulatum
Discovered
2004 · Tasiemski et al.
Theromyzin molecular structure

Biological Targets

  • → bacterial membranes (broad-spectrum)

Key Citations

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

External Resources

    Related Antimicrobial Compounds

    Theromacin

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

    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.