434 Salivary Proteins — Integrated Proteomics of Hirudo medicinalis

The largest published catalog of leech salivary bioactive compounds

Genomics & ProteomicsLiu et al. (2019)— Journal of ProteomicsDOI →

Why This Matters for Hirudotherapy

Vastly expanded the known bioactive molecule catalog from ~20 classically characterized compounds to 434+. Provides the foundation for modern drug discovery from the leech secretome and explains the multi-target therapeutic mechanism.

Investigational / Research Priority

Basic science research. This review covers proteomics and transcriptomics findings with no direct clinical application at this stage.

Last Updated: May 27, 2026Reviewed by: Andrei Dokukin, MD

Salivary proteomicsDiscovery science

From 20 compounds to 434 proteins

For over a century, our understanding of leech salivary gland secretion composition was limited to approximately 20 compounds isolated through classical biochemistry — hirudin, calin, destabilase, hyaluronidase, bdellins, and eglins being the best characterized. Liu et al. (2019) transformed this picture using integrated proteomics and transcriptomics, revealing that the medicinal leech secretome is vastly more complex than previously understood.[R1]

2025–2026 update: catalog now 440+ identifications

The 434-protein figure reflects the Liu et al. (2007) landmark plus Hildebrandt & Lemke (2011) refinements. Manuvera et al. (2025) and Serebrennikova et al. (2025) have since expanded the curated proteome to 440+ identifications, with additional isoforms in validation. The six functional categories, methodology, and quantitative impact statistics below remain anchored on the historically annotated set; the newer additions extend rather than overturn this catalogue.

Methodology

The study combined two complementary omics approaches:

Proteomics (protein-level)

Liquid chromatography–tandem mass spectrometry (LC-MS/MS) of salivary gland secretions identified 434 full-length protein sequences, of which 44 were confirmed as bioactive through functional annotation.

Transcriptomics (RNA-level)

RNA sequencing of salivary gland tissue identified 221 bioactive transcripts, providing evidence that the gland actively expresses a vast repertoire of functional molecules beyond what had been characterized.

[R1]

Six functional categories

The 434 identified proteins were classified into six major functional groups, revealing the multi-target nature of leech salivary gland secretion:

Anticoagulants

Thrombin inhibitors (hirudin variants), Factor Xa inhibitors, fibrinolytic enzymes. The primary functional group responsible for the sustained bleeding effect.

Anti-platelet

Platelet aggregation inhibitors (calin, saratin) and collagen adhesion blockers. Prevent primary hemostasis at the bite wound.

Vasodilators

Histamine-like compounds, acetylcholine, and vasodilatory peptides that increase local blood flow to the feeding site.

Anti-inflammatory

Proteinase inhibitors (bdellins, eglins), complement inhibitors, and immune modulators that suppress the host inflammatory response.

Analgesic

Anesthetic and analgesic compounds that reduce pain at the bite site — explaining why patients often do not feel the initial attachment.

Antimicrobial

Antimicrobial peptides (theromacin, destabilase-lysozyme, hirunipins) that protect the wound environment from secondary infection.

[R1]

Quantitative impact

434

Proteins identified

Confirmed bioactive

221

Bioactive transcripts

Functional categories

Why this matters for hirudotherapy

The Liu et al. study fundamentally changed our understanding of how leech therapy works. Instead of a simple anticoagulant effect (the hirudin-centric model), we now understand that the leech delivers a coordinated multi-target pharmacological cocktail — simultaneously acting on coagulation, platelets, vasculature, inflammation, pain, and infection. This multi-target mechanism may explain the broad therapeutic effects observed clinically, including the prolonged pain relief seen in osteoarthritis trials.[R1]

The dataset also provides a rich source for drug discovery: the vast majority of the 434 proteins remain uncharacterized for therapeutic potential, representing a largely untapped pharmacological resource.[R2][R3]

Complementary genomic data

The Kvist et al. (2020) genome assembly provides the genomic framework that complements this proteomic catalog. Together, these two studies form the foundation of modern leech bioprospecting — enabling identification of novel compounds at the gene, transcript, and protein levels simultaneously.

References

[R1]
Integrated Proteomics and Transcriptomics of Hirudo medicinalis Salivary Gland Secretion
Journal of Proteomics(2019)https://doi.org/10.1016/j.jprot.2019.01.016
Primary source. First integrated multi-omics study of leech salivary glands.
[R2]
A Chromosome-Level Genome Assembly for the Medicinal Leech and Identification of Anticoagulant Genes
Scientific Reports(2020)https://doi.org/10.1038/s41598-020-58842-4
Kvist et al. genome assembly complementing the proteomics data.
[R3]
Comparative Transcriptomics of Three Hirudo Species: Insights into Evolution of Salivary Proteins
BMC Genomics(2020)https://doi.org/10.1186/s12864-020-6748-0
Babenko et al. cross-species comparison of salivary transcriptomes.

← All research articles