The kallikrein-related peptidase (KLK) family consists of 15 secreted serine proteases (KLK1–KLK15) that are produced as inactive zymogens. After cleavage of their N-terminal pro-peptide, these enzymes become catalytically active and participate in tightly regulated proteolytic cascades. KLKs are widely studied in cancer biology, inflammatory disease, and neurological disease research such as Alzheimer’s disease. Their activity contributes to extracellular matrix remodelling, cytokine processing, and maintenance of tissue homeostasis.
| Attribute | Specification |
|---|---|
| Protein Family | Kallikrein-related serine proteases (KLK1–KLK15) |
| Expression System | Mammalian HEK293 cells |
| Protein Forms | Active enzymes and pro-forms |
| Purity | >95% by SEC-HPLC |
| Endotoxin Level | <0.01 EU/μg |
| Activity Validation | Fluorogenic peptide substrate cleavage assay |
| Applications | Enzyme activity assays, inhibitor screening, antibody discovery, biomarker research |
| Tags Available | His, Flag, Avi, Biotin |
| Species Options | Human and multi-species variants |
KLK - as Therapeutic Target in Desease
Dysregulation of KLK expression or activity is strongly linked to multiple pathologies including:
- Cardiovascular Disease
- Cancer (Prostate, Ovarian, Breast)
- Skin Disorders (e.g. Atopic Dermatitis, Netherton syndrome, etc.)
- Neurodegenerative Diseases (e.g. Alzheimer's Disease, Multiple Sclerosis, etc.)
- Airway Diseases (e.g. asthma, chronic bronchitis)
Tissue kallikreins and plasma kallikrein-related pathways contribute to inflammatory signaling, including kinin-mediated pathways such as bradykinin receptor activation. Separately, kallikrein-related peptidases are studied for their roles in protease cascades, tissue remodeling, barrier function, and disease-associated proteolysis.
KLK genes are expressed as enzymatically inhibited zymogens
https://doi.org/10.1038/nrd4534
Aberrant KLK activity has been linked to airway disease progression and broader disruption of extracellular protease networks. KLKs interact with other proteolytic enzymes, including matrix metalloproteinases, mast cell chymase, and carboxypeptidase A, forming interconnected pathways that influence inflammatory signalling and tissue remodelling.
Comprehensive Collection of KLK Enzymes
We offer most KLKs in both pro-form and enzymatically active forms (with more coming soon!), enabling simpler processing and faster functional studies.
Product Applications:
Drug & Antibody discovery:
Immunization
In Vitro Antibody/Inhibitor Screening
Antibody Affinity & Epitope Binning
Structural Characterization
Interaction & Kinetic Analysis
Binding Kinetics - SPR / BLI
Quantitative Immunoassays - ELISA
Cell-based Functional Assays
Product Features:
→ High protein binding affinity
→ Enzymatic activity data
→ Ultra-low endotoxin (<0.01 EU/μg) - critical for cell-based assays and in vivo studies
→ Mammalian Expression
→ Various tags (His, Flag, Biotin, etc.)
→ Multi-Species options, ideal for cross-species validation
Product Validation
KLK5: Regulator of Skin Homeostasis
KLK5 is a key serine protease primarily expressed in the epidermis, where it serves as a master initiator of the enzymatic cascade that regulates skin desquamation. By activating secondary proteases like KLK7, it maintains the delicate balance of the skin barrier. Its dysregulation is a central driver in inflammatory conditions such as Netherton syndrome, atopic dermatitis, and rosacea.
See our blog on the therapeutic landscape of KLK5/7 in these skin diseases →
Immobilized Human Kallikrein 5, His Tag at 0.5ug/ml (100ul/Well) on the plate. Dose response curve for Anti-Kallikrein 5 Antibody, hFc Tag with the EC50 of 3.7ng/ml determined by ELISA (QC Test).
The purity of Human Kallikrein 5 is greater than 95% as determined by SEC-HPLC.
Measured by its ability to cleave the fluorogenic peptide substrate Boc-VPR-AMC. The specific activity is >400 pmol/min/µg (QC Test).
Loaded Anti-Kallikrein 5 Antibody, hFc Tag on ProA-Biosensor can bind Human Kallikrein 5, His Tag with an affinity constant of 1.23 nM as determined in BLI assay (Gator® Prime).
KLK2: New Target for Prostate Cancer
KLK2 (hK2) is a highly prostate-specific serine protease that shares 80% amino acid homology with PSA (KLK3) and acts as its primary physiological activator. Regulated by androgen receptor signaling, it is overexpressed throughout the prostate cancer disease continuum (including metastatic castration-resistant stages) where it facilitates tumor growth, migration, and angiogenesis. Beyond its role as a diagnostic biomarker, the recent discovery of its cell surface expression has established KLK2 as a promising therapeutic target for radioligand and CAR T-cell therapies.
See our blog on the latest clinical developments of KLK2 drugs in Prostate Cancer →
Immobilized Biotinylated Human Kallikrein 2, His Avi Tag at 0.5ug/ml (100ul/well) on the streptavidin precoated plate (5ug/ml). Dose response curve for Anti-Kallikrein 2 Antibody, hFc Tag with the EC50 of 28.0ng/ml determined by ELISA.
The purity of Biotinylated Human Kallikrein 2 is greater than 95% as determined by SEC-HPLC.
Measured by its ability to cleave the fluorogenic peptide substrate Boc-VPR-AMC. The specific activity is >400 pmol/min/µg (QC Test).
Loaded Anti-Kallikrein 2 Antibody, hFc Tag on ProA-Biosensor can bind Biotinylated Human Kallikrein 2, His-Avi Tag with an affinity constant of 1.89 nM as determined in BLI assay (Gator® Prime).
Resources
Check out our blogs and informational content for a deeper dive into KLK enzyme proteins:
Custom KLK Proteins
Our team can modify parameters such as mutations, tags, biotinylation, and fluorescent labels, to ensure the product aligns with your precise requirements. This option provides a cost-effective and efficient solution by leveraging our established product base while meeting your unique specifications.
Custom Protein Services
Research Applications of KLK Proteins
Kallikrein-related proteases are widely used as biochemical tools in studies investigating protease signalling, inflammatory pathways, and tumour microenvironment biology. Recombinant KLK proteins allow researchers to investigate enzymatic activity, substrate specificity, and downstream proteolytic cascades under controlled experimental conditions.
Common research applications include:
Cancer biomarker research
Several members of the KLK family function as diagnostic and prognostic biomarkers in oncology. KLK3 (prostate-specific antigen) and KLK2 are extensively studied in prostate cancer biology, while other KLKs have been linked to ovarian, breast, and pancreatic cancers.
Inflammatory disease studies
KLK activity contributes to inflammatory signalling pathways involved in skin barrier function and airway inflammation. KLK5 and KLK7, for example, are strongly associated with conditions such as atopic dermatitis and Netherton syndrome.
Protease cascade analysis
KLK enzymes regulate interconnected protease networks that influence extracellular matrix remodelling and cytokine activation. Recombinant proteins allow researchers to dissect these cascades through enzymatic assays and substrate cleavage studies.
Drug discovery and inhibitor screening
Because KLK dysregulation contributes to disease progression, these enzymes are frequently used in small-molecule inhibitor screening and therapeutic antibody development programs.
FAQs About KLK Active Enzymes
KLK proteins are naturally synthesized as inactive zymogens and require proteolytic cleavage of the pro-peptide region to become catalytically active. Active KLK enzymes in this category are pre-cleaved and functionally validated, enabling immediate use in enzymatic activity assays, inhibitor screening, and binding studies without additional activation steps across the broader KLK family.
Each active KLK protein is tested using a fluorogenic peptide substrate cleavage assay. Specific activity values are determined and documented during quality control testing to ensure consistent catalytic performance across production lots. This validation ensures reliability for kinetic analysis and drug discovery workflows targeting members of the KLK family and the broader KLK protease network.
Endotoxin contamination can trigger immune signaling pathways and interfere with cell-based assays or in vivo studies. Ultra-low endotoxin KLK enzymes (<0.01 EU/μg) reduce the risk of non-specific inflammatory responses, particularly in models involving inflammatory mediators, mast cell signaling, and tissue kallikrein pathways.
All recombinant KLK active enzymes are produced in mammalian HEK293 cells, supporting proper folding and functional activity. Mammalian expression supports proper protein folding, post-translational modifications, and enzymatic conformation, which are critical for maintaining physiological activity and accurate functional results across the broader tissue kallikrein network.
KLK active enzymes are purified to greater than 95% purity as confirmed by SEC-HPLC. High purity minimizes background interference in binding, kinetic, and structural studies.
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Recombinant KLK Active Enzymes (KLK1–KLK15) | KACTUS Bio