Table of contents

Applications and use cases
EDTA-free protease inhibitor cocktails
Protease and phosphatase inhibitor cocktails
PMSF (serine protease inhibitor)
Types of protease inhibitors and their targets
How protease inhibitors work
Protease inhibitor selection guide
Choosing inhibitors based on sample type
Protease inhibitor formats
Protease inhibitor cocktail composition
Dilution and usage guidance
FAQ and featured products

Protease inhibitor cocktails are essential tools in protein research, designed to prevent protein degradation during sample preparation by inhibiting the activity of proteases. These reagents are crucial for maintaining the integrity of proteins in various samples, allowing for more accurate analysis in downstream applications such as western blot, mass spectrometry, and immunoprecipitation. Our protease inhibitor cocktails are formulated to be broad-spectrum, easy-to-use, and highly effective, making them ideal for a wide range of biological samples.

Composition and mechanism

Our protease inhibitor cocktails contain a blend of inhibitors that target a wide range of protease classes, including serine proteases, cysteine proteases, aspartic proteases, and metalloproteases. This comprehensive protection helps preserve the native state and function of proteins by inhibiting proteolytic degradation.

Easy-to-use formats

We offer these inhibitors in various formats, including ready-to-use cocktail liquid solutions or individual powder format . This flexibility allows researchers to choose the format that best suits their experimental needs.

Compatibility and stability

Designed to be compatible with common buffer systems and sample types, our protease inhibitor cocktails do not interfere with protein quantification methods or other analytical assays.

Applications and use cases

Cell lysis for protein extraction

Adding protease inhibitor cocktails during cell lysis protects proteins from degradation, ensuring optimal protein stability for analysis.

Tissue homogenization

Especially crucial in tissues with high protease activity, these inhibitors protect proteins during the homogenization process.

Immunoprecipitation and co-immunoprecipitation

Protease inhibitors are vital to maintain the integrity of protein-protein complexes during these procedures.

Protein purification and concentration

During purification steps, inhibitors help prevent degradation, preserving the functionality and structure of the protein of interest.

EDTA-free protease inhibitor cocktails

EDTA-free protease inhibitor cocktails are designed for applications where metal chelation must be avoided. While EDTA is commonly included in inhibitor formulations to block metalloproteases, it can interfere with metal-dependent proteins, enzymes, and downstream analytical techniques.

Using an EDTA-free formulation ensures that metalloproteins remain active and structurally intact, making these inhibitors particularly important for sensitive assays and workflows.

When to use EDTA-free protease inhibitors

EDTA-free protease inhibitor cocktails are recommended for:

• Metalloprotease-sensitive assays where metal ions are required for enzyme activity
• Isoelectric focusing (IEF) and other techniques where EDTA may disrupt protein separation
• Mass spectrometry (MS) workflows, where EDTA can interfere with sample preparation and analysis
• Experiments involving metal-binding proteins or cofactors

In these applications, EDTA-free inhibitors provide effective protection against proteolysis without compromising assay performance or downstream compatibility.

Browse EDTA-free protease inhibitor cocktails

Protease and phosphatase inhibitor cocktails

Protease and phosphatase inhibitor cocktails are designed to protect both protein integrity and phosphorylation status during sample preparation. While protease inhibitors prevent degradation, phosphatase inhibitors preserve phosphorylation by blocking enzymatic dephosphorylation.

Using a combined inhibitor cocktail is essential when studying phosphorylated proteins, as both degradation and dephosphorylation can occur rapidly during cell lysis and extraction. For these workflows, protease inhibitors are often used alongside phosphatase inhibitors to preserve protein modification states.

When to use combined inhibitor cocktails

Protease and phosphatase inhibitor cocktails are recommended for:

• Phosphoprotein analysis, including signalling pathway studies
• Western blotting of phosphorylated targets (eg phospho-specific antibodies)
• Kinase and phosphatase activity assays
• Cell signalling and proteomics workflows

In these applications, combining protease and phosphatase inhibitors helps ensure that both protein abundance and modification state are accurately preserved, leading to more reliable and reproducible results.

Explore phosphatase inhibitor cocktails and reagents

PMSF (serine protease inhibitor)

Phenylmethylsulfonyl fluoride (PMSF) is a commonly used serine protease inhibitor that irreversibly inhibits enzymes such as trypsin and chymotrypsin. It is frequently used during cell lysis to prevent proteolytic degradation, particularly in workflows where serine proteases are the primary concern.

Working concentration and preparation

PMSF is typically used at a final concentration of 0.5 mM in lysis buffers.

• Commonly prepared as a stock solution in ethanol or isopropanol
• Added to fresh lysis buffers immediately before use due to its instability in aqueous solutions
• Should be handled with care, as PMSF is toxic and rapidly degrades in water

When to use PMSF vs inhibitor cocktails

PMSF can be used as a standalone inhibitor in simple applications, but it is often combined with other inhibitors for broader protection.

• Use PMSF alone when targeting serine proteases specifically
• Use protease inhibitor cocktails when working with complex samples containing multiple protease classes
• Cocktails provide broader coverage, including cysteine, aspartic, and metalloproteases

For most applications, protease inhibitor cocktails are recommended to ensure comprehensive protection against proteolysis, while PMSF can be used as a targeted or supplementary inhibitor.

Types of protease inhibitors and their targets

Protease inhibitor cocktails typically contain a combination of inhibitors that target different classes of proteases. Understanding how individual inhibitors function can help you select the most appropriate formulation for your experiment and ensure comprehensive protection against proteolysis.

By combining inhibitors that target serine, cysteine, aspartic, and metalloproteases, protease inhibitor cocktails provide broad-spectrum protection during cell lysis and protein extraction. This ensures that proteins remain intact and suitable for downstream applications such as western blotting, immunoprecipitation, and mass spectrometry.

How protease inhibitors work

Protease inhibitors work by blocking the activity of proteolytic enzymes, preventing them from breaking down proteins during sample preparation. Different classes of inhibitors use distinct mechanisms of action, which determine how they interact with target enzymes and how long their effects last.

Serine protease inhibitors

Typically act as irreversible inhibitors, forming covalent bonds with the active site of the enzyme and permanently inactivating it.

Cysteine protease inhibitors

Often irreversibly inhibit proteases by reacting with the catalytic cysteine residue, preventing further enzymatic activity.

Aspartic protease inhibitors

Generally act as reversible inhibitors, binding non-covalently to the enzyme and blocking substrate access.

Metalloprotease inhibitors

Function by chelating metal ions that are essential for enzyme activity and blocking substrate access.

Aminopeptidase inhibitors

Typically act as reversible inhibitors, interfering with enzyme activity at the substrate-binding site.

Protease inhibitor selection guide

Selecting the right protease inhibitor depends on the types of proteases present in your sample. Because different proteases target different proteins in different ways, combining inhibitors that cover multiple protease classes is often essential for effective protection during cell lysis and protein extraction.

For most applications, broad-spectrum protease inhibitor cocktails are recommended, as they combine inhibitors targeting multiple protease classes. However, for specialized workflows, such as metalloprotease-sensitive assays or mass spectrometry, selecting an EDTA-free formulation may be more appropriate.

Choosing inhibitors based on sample type

Protease activity can vary significantly depending on the sample type, making it important to select an appropriate inhibitor strategy for your experiment. Different biological materials contain distinct protease profiles, which can influence both the rate and type of protein degradation during sample preparation.

Mammalian cell lysates

Typically contain a broad range of proteases, including serine, cysteine, and metalloproteases. A broad-spectrum protease inhibitor cocktail is generally recommended to ensure comprehensive protection during lysis.

Tissue homogenates

Often exhibit higher protease activity due to the presence of multiple cell types and extracellular enzymes. Strong, multi-class inhibitor cocktails, sometimes combined with phosphatase inhibitors, are recommended for effective protection.

Bacterial extracts

Protease profiles differ from mammalian systems and may require targeted inhibitors depending on the expression system used. In some cases, EDTA-containing inhibitors may be beneficial to suppress metalloprotease activity.

Protease inhibitor formats

Protease inhibitor cocktails are available in several formats, including liquid concentrates, tablets, and lyophilised powders. Each format offers different advantages depending on your workflow, preparation time, and experimental requirements.

Liquid 100X protease inhibitor cocktails are often preferred for routine workflows due to their ease of use and rapid preparation, particularly in time-sensitive experiments. Tablet and lyophilised formats offer greater stability and convenience for storage, making them suitable for labs that require longer shelf life or less frequent use.

Selecting the right format depends on your workflow priorities, including speed, flexibility, and storage requirements.

Protease inhibitor cocktail composition

Protease inhibitor cocktails are formulated by combining multiple inhibitors that target different classes of proteases. While exact compositions may vary between products, most broad-spectrum cocktails include a defined set of inhibitors to ensure comprehensive protection during sample preparation.

For example, Protease Inhibitor Cocktail (100X) contains:
AEBSF (Serine protease inhibitor)
Aprotinin (Serine protease inhibitor)
Bestatin (Aminopeptidase inhibitor)
E-64 (Cysteine protease inhibitor)
Leupeptin (Serine/Cysteine protease inhibitor)
Pepstatin A (Aspartic acid protease inhibitor)
EDTA (Metalloprotease inhibitor)

Some protease inhibitor cocktails have the same composition but without the EDTA. These are used if the downstream application is sensitive to metal chelators (like His-tag purification or certain enzyme assays).

Dilution and usage guidance

Protease inhibitor cocktails are typically supplied as concentrated solutions and should be diluted according to a working concentration immediately before use. A common approach is to add the inhibitor cocktail at 1:100 dilution directly to your lysis buffer or sample preparation solution.

Best practice workflow

Add immediately before lysis

Add the protease inhibitor cocktail just before or during cell lysis to maximise effectiveness.

Keep samples cold

Work on ice at 4 degrees Celsius and use pre-chilled buffers to minimise protease activity.

Mix thoroughly

Ensure even distribution throughout the sample for consistent protection.

Use fresh solutions and handle correctly

Prepare inhibitors fresh where possible and avoid repeated freeze-thaw cycles.

Always refer to product-specific datasheets for recommended working concentrations and compatibility with your experimental conditions.

Protease inhibitors are typically added directly to your lysis buffer immediately before use to prevent protein degradation during extraction. Explore our range of lysis buffers to support your sample preparation workflow.

Dilution and usage guidance

Protease inhibitor cocktails are typically supplied as concentrated solutions and should be diluted according to a working concentration immediately before use. A common approach is to add the inhibitor cocktail at 1:100 dilution directly to your lysis buffer or sample preparation solution.

Best practice workflow

Add immediately before lysis

Add the protease inhibitor cocktail just before or during cell lysis to maximise effectiveness.

Keep samples cold

Work on ice at 4 degrees Celsius and use pre-chilled buffers to minimise protease activity.

Mix thoroughly

Ensure even distribution throughout the sample for consistent protection.

Use fresh solutions and handle correctly

Prepare inhibitors fresh where possible and avoid repeated freeze-thaw cycles.

Always refer to product-specific datasheets for recommended working concentrations and compatibility with your experimental conditions.

Protease inhibitors are typically added directly to your lysis buffer immediately before use to prevent protein degradation during extraction. Explore our range of lysis buffers to support your sample preparation workflow.

FAQ