Biological Background and Function of KLK5

Kallikrein 5 (KLK5), also known as kallikrein-related peptidase 5 or stratum corneum tryptic enzyme (SCTE), is a secreted serine protease belonging to the kallikrein-related peptidase (KLK) family, which comprises 15 members (KLK1–KLK15) encoded in a gene cluster on chromosome 19q13.4 in humans.

KLK5 exhibits trypsin-like activity, cleaving peptide bonds preferentially at the C-terminal side of arginine and lysine residues. Within the epidermis, KLK5 is expressed predominantly in the stratum granulosum and stratum corneum, where it plays a central role in the proteolytic cascade governing desquamation — the regulated shedding of corneocytes from the skin surface. KLK5 activates other KLK family members, including KLK7 and KLK14, establishing it as an upstream regulator of a broader kallikrein protease network.

Dysregulation of KLK5 activity has been implicated in several skin pathologies. In Netherton syndrome, a rare genetic disorder caused by loss-of-function mutations in SPINK5 (encoding the serine protease inhibitor LEKTI), uncontrolled KLK5 activity leads to excessive desquamation, skin barrier defects, and atopic manifestations. KLK5 is also being investigated as a biomarker and potential therapeutic target in certain epithelial cancers.

Biochemical Properties and Recombinant Protein Considerations

Recombinant Human Kallikrein 5 Protein (SKU: rp368170) is produced using recombinant expression technology to deliver a well-characterized, research-grade serine protease for in vitro studies. The following biochemical considerations are important for experimental design:

• Protease Class: Serine protease; catalytic triad composed of His, Asp, and Ser residues, characteristic of the chymotrypsin superfamily.
• Substrate Specificity: Trypsin-like; cleaves after Arg and Lys residues. Synthetic fluorogenic substrates such as Boc-Val-Pro-Arg-AMC or Tos-Gly-Pro-Arg-pNA are commonly used for activity assays.
• Zymogen Activation: KLK5 is synthesized as an inactive zymogen (pro-KLK5) requiring proteolytic activation. Recombinant preparations may be supplied as the active enzyme or as the zymogen depending on the product format; consult the product datasheet for clarification.
• Inhibitors: Activity is inhibited by LEKTI domains, α2-macroglobulin, and classical serine protease inhibitors such as PMSF and aprotinin. Including appropriate inhibitor controls in assays is recommended.
• Glycosylation: KLK5 is a glycoprotein; glycosylation status may differ between expression systems (e.g., mammalian vs. bacterial), potentially affecting specific activity and folding.

Always verify activity and purity data provided in the Certificate of Analysis (CoA) before use, and perform a small-scale activity validation assay upon first use of a new lot.

Handling, Storage, and Reconstitution Protocol

Proper handling and storage of Recombinant Human Kallikrein 5 Protein are essential to maintain enzymatic activity and prevent degradation. Follow the guidelines below and always refer to the product-specific datasheet (rp368170) for lot-specific instructions.

Reconstitution

• Briefly centrifuge the vial before opening to consolidate lyophilized material.
• Reconstitute in sterile, ultrapure water or an appropriate buffer (e.g., 50 mM Tris-HCl, pH 8.0, 150 mM NaCl) to the recommended concentration as stated in the CoA.
• Allow the solution to sit for 5–10 minutes at room temperature with gentle swirling; avoid vigorous vortexing to prevent denaturation.
• Filter sterilize if required for cell-based assays.

Storage

• Store lyophilized protein at –20 °C or –80 °C, protected from moisture and light.
• Once reconstituted, aliquot into single-use volumes to avoid repeated freeze-thaw cycles, which can significantly reduce activity.
• Reconstituted protein should be stored at –80 °C for long-term storage or at 4 °C for short-term use (up to 1 week); add a carrier protein (e.g., 0.1% BSA) if storing dilute solutions.

Working Conditions

• Use low-binding tubes and pipette tips to minimize adsorption losses at low protein concentrations.
• Optimal assay conditions (pH, temperature, ionic strength, cofactors) should be validated empirically; consult the product datasheet for suggested starting conditions.

Research Applications

Recombinant Human Kallikrein 5 Protein is a versatile research reagent applicable across multiple scientific disciplines:

• Skin Biology and Desquamation Research: KLK5 is used to study the proteolytic events underpinning normal skin shedding and to model pathological conditions such as Netherton syndrome, Comel-Netherton syndrome variants, and atopic dermatitis where the KLK/LEKTI axis is disrupted.
• Protease Substrate Profiling: Used in degradomics and proteomic studies to identify and characterize KLK5 substrates in the extracellular matrix and on the cell surface, including corneodesmosin, desmoglein-1, and other structural proteins.
• Enzyme Kinetics and Inhibitor Screening: Suitable for determining kinetic parameters (Km, Vmax, kcat) and for high-throughput or medium-throughput screening of serine protease inhibitors as potential therapeutics.
• Kallikrein Cascade Studies: Enables dissection of the KLK activation cascade, particularly the role of KLK5 in activating KLK7 and KLK14, to understand feedforward protease amplification in skin.
• Cancer Biomarker Research: KLK5 is elevated in certain ovarian, breast, and other epithelial cancers; recombinant protein is used in ELISA development, antibody validation, and functional studies.
• Structural and Biophysical Studies: Used in crystallography, hydrogen-deuterium exchange mass spectrometry (HDX-MS), and other structural biology approaches to characterize the enzyme's active site and inhibitor-binding modes.

Quality Assurance and Ordering Information

Aladdin Scientific's Recombinant Human Kallikrein 5 Protein (SKU: rp368170) is manufactured and quality-controlled to meet the demands of rigorous research applications.

Quality Control

• Each lot is tested for purity (typically by SDS-PAGE and/or HPLC), identity (e.g., Western blot or mass spectrometry), and biological activity (enzyme activity assay).
• A Certificate of Analysis (CoA) is provided with each shipment and contains lot-specific data for all QC parameters.
• Endotoxin levels are measured and controlled; consult the CoA for lot-specific values, particularly important for cell-based assays.

Ordering

• SKU: rp368170
• Product Name: Recombinant Human Kallikrein 5 Protein
• Contact Aladdin Scientific customer service or visit the product page for current pricing, available quantities, and lead times.
• Bulk quantities and custom formulations may be available upon request.

Shipping and Storage on Receipt

• The protein is typically shipped on dry ice; inspect the package upon receipt and confirm that the product remains frozen or in the appropriate physical state.
• Transfer immediately to –80 °C storage upon receipt unless immediate use is planned.