KLK5 Human
Description
Molecular Structure and Expression
Kallikrein-related peptidase 5 (KLK5) is a serine protease encoded by the KLK5 gene located on chromosome 19q13.41. It is synthesized as a preproenzyme containing:
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A 29-amino acid signal peptide (Met1–Gly22)
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A 37-amino acid propeptide (Val23–Arg66)
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A mature enzyme (Ile67–Ser293) with a molecular mass of ~27–28 kDa .
KLK5 is glycosylated and expressed in epithelial tissues, including the skin, breast, brain, and reproductive organs, with elevated levels in ovarian, cervical, and breast cancers .
Biochemical Activity and Substrate Specificity
KLK5 exhibits trypsin-like activity, preferentially cleaving substrates with arginine at the P1 position . Key biochemical features include:
KLK5 activity is regulated by serine protease inhibitors (serpins) and environmental pH .
Skin Homeostasis and Disease
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Desquamation: KLK5 degrades corneodesmosomal proteins (e.g., desmoglein 1) in the stratum corneum, enabling epidermal shedding .
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Inflammation: Unregulated KLK5 in Netherton syndrome triggers PAR2-mediated NF-κB signaling, upregulating TSLP, IL-8, and TNF-α, leading to atopic dermatitis .
Cancer Progression
Infectious Disease
KLK5 primes SARS-CoV-2 and MERS-CoV spike proteins, enhancing viral entry. Inhibition reduces viral replication and lung inflammation .
Therapeutic Targeting and Diagnostic Potential
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Inhibitors: LEKTI fragments (skin disorders), small-molecule serine protease inhibitors (COVID-19) .
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Biomarker: Elevated KLK5 in serum or tumor tissue predicts poor outcomes in ovarian and cervical cancers .
Research Gaps and Future Directions
Product Specs
Q&A
KLK5 (Kallikrein-Related Peptidase 5) is a serine protease with critical roles in skin physiology and cancer progression. Below are structured FAQs addressing key research considerations, supported by experimental evidence from peer-reviewed studies.
Advanced Research Questions
How to resolve contradictions in KLK5's prognostic significance across cancers?
KLK5 shows dual roles:
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Ovarian cancer: High mRNA expression correlates with reduced median survival (23 vs. 41 months in KLK5-negative tumors, p < 0.01) .
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Breast cancer: Metaplastic TNBC exhibits 3.2-fold higher KLK5 expression vs. non-metaplastic TNBC (GSE76275 dataset), but no survival correlation .
Methodological recommendation: Perform cohort stratification by hormone receptor status and histological subtype. Use multivariate Cox regression adjusting for age, stage, and treatment modality.
What optimization strategies improve KLK5 activity assays?
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Substrate kinetics: Use Boc-Val-Pro-Arg-AMC (200 μM) in 50 mM Tris/0.005% Brij-35 (pH 8.0). Measure fluorescence (Ex/Em: 380/460 nm) for 5 min. Adjust enzyme concentration to 0.1–0.8 μg/well for linear kinetics .
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Inhibition controls: Include 10 μM leupeptin (serine protease inhibitor) to confirm specificity. Activity reduction >90% validates assay integrity .
How does KLK5 interact with Th17 cells in metabolic disease?
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Mechanism: KLK5 induces DPP4 shedding from CD4+ Th17 cells via proteolytic cleavage (KM = 18 μM). Use flow cytometry with anti-CD26 antibodies to quantify membrane DPP4 loss .
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Disease link: T2DM patient-derived Th17 cells show 2.5-fold higher KLK5 secretion vs. controls (p = 0.007). Neutralize with α-KLK5 antibodies (10 μg/mL) to restore DPP4 levels .
Technical Challenges & Solutions
Addressing KLK5 autoactivation in functional studies
Validating KLK5-specific antibodies
Multi-Omics Integration
Correlating KLK5 expression with genomic alterations
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TCGA analysis: 18% of KLK5-high ovarian tumors have Chr19q13.4 amplifications (log2 ratio >0.3). Use cBioPortal’s OncoPrint to visualize co-occurrence with BRCA1 mutations .
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Methylation: Hypermethylation at cg08323415 (KLK5 promoter) reduces mRNA by 60% in ER+ breast cancer (Illumina 450K array data) .
Product Science Overview
The human KLK5 gene encodes a protein that consists of a signal peptide (Met1 to Gly22), a pro region (Val23 to Arg66), and a mature/active enzyme (Ile67 to Ser293) . The mature form of KLK5 is responsible for its proteolytic activity. KLK5 is initially synthesized as an inactive zymogen and requires proteolytic cleavage to become active .
KLK5 is predominantly expressed in the skin, particularly in the stratum corneum, where it plays a crucial role in the degradation of corneodesmosomes, leading to skin desquamation . This process is essential for maintaining skin homeostasis and barrier function. Additionally, KLK5 has been implicated in various pathological conditions, including atopic dermatitis, rosacea, and certain types of cancer .
Recombinant human KLK5 is produced using advanced biotechnological methods. It is typically expressed in a mouse myeloma cell line (NS0) and purified to high levels of purity (>95%) using SDS-PAGE under reducing conditions . The recombinant protein is often tagged with a C-terminal 10-His tag to facilitate purification and detection .
The activity of recombinant KLK5 is measured by its ability to cleave specific fluorogenic peptide substrates, such as Boc-VPR-AMC . This activity is quantified in terms of specific activity, which is typically greater than 200 pmol/min/µg .
Recombinant KLK5 is widely used in research to study its role in skin physiology and pathology. It is also utilized in the development of therapeutic interventions for skin disorders and certain cancers. The availability of high-purity recombinant KLK5 allows researchers to investigate its biochemical properties, substrate specificity, and potential inhibitors .
