Many researchers working on Cathepsin B/L projects have had similar experiences:

• Western blot and qPCR were both done, showing the protein is "present" and "highly expressed"

• But when moving to functional assays, the phenotype does not match expectations

• Kits are like black boxes; it's hard to build your own enzyme activity model from scratch

The reason is that the expression level of proteases such as Cathepsin does not fully equate to actual enzyme activity.

Proteases are synthesized as inactive zymogens within cells and require proteolytic cleavage to become active. Western blot measures total protein (including zymogen and mature enzyme), while qPCR reflects transcription levels – they can tell you "how much" is present, but cannot directly answer "how much is in an active state."

To develop detection reagents, screen inhibitors, and build a reproducible and scalable in vitro evaluation system, what you need is not a "ready-made result" but a reliable, classic, and controllable – fluorescent substrate pathway.

Z-Phe-Arg-4MβNA·HCl (CAS: 100900-17-2) is a 4MβNA (4-methoxy-β-naphthylamide)-labeled peptide fluorescent substrate, consisting of three parts:

• Z-: N-terminal protecting group, part of the substrate structure

• Phe-Arg: classic recognition sequence for Cathepsin B/L

• 4MβNA: reporter group that produces a fluorescent signal upon enzymatic cleavage

The working principle is as follows:

1. Under appropriate buffer conditions, cysteine proteases such as Cathepsin B/L/S recognize the Phe-Arg sequence and cleave near the Arg site.

2. After cleavage, 4MβNA is released, generating a detectable fluorescent signal in the corresponding detection system, thereby reflecting protease activity.

3. By monitoring changes in the detection signal, the degree of substrate hydrolysis and protease activity can be analyzed.

In simple terms: the more active the enzyme, the faster the cleavage, and the stronger the fluorescence signal. After adding candidate inhibitors, the effect on protease activity can be evaluated by monitoring changes in the signal.

Because the P1 site is Arg, the substrate can also be recognized by some trypsin-like serine proteases, including:

• Plasma Kallikrein

• Plasmin

• Trypsin

• Other Arg-specific serine proteases

Therefore, the Z-Phe-Arg-4MβNA substrate can serve both the cathepsin family and trypsin-like serine protease detection systems.

Chinese Name: Z-Phe-Arg-4MβNA · Hydrochloride

English Name: Z-Phe-Arg-4MβNA Hydrochloride

Abbreviation: Z-Phe-Arg-4MβNA · HCl

CAS Number: 100900-17-2

Molecular Formula: C34H39ClN6O5

Molecular Weight: 647.17

Specifications: 1 g / 5 g / 25 g (Custom packaging supported)

Form: Off-white crystalline powder

Product Number: G04030017

Signal: Fluorescence

As a classic substrate validated through long-term literature, Z-Phe-Arg-4MβNA can support three typical application scenarios:

1. Development of Cathepsin B/L/S enzyme activity detection reagents

Used to establish quantitative analysis methods for protease activity, supporting the development of cathepsin detection kits, related enzyme activity assay systems, and high-throughput detection platforms.

Can address the following development needs:

• Establishment of Cathepsin B/L/S activity detection methods

• R&D of cathepsin detection kits

• Construction of high-throughput detection platforms

2. Cathepsin inhibitor screening and drug development

Build an evaluation model for cathepsin enzyme activity for studying and evaluating the inhibitory activity of candidate compounds.

Typical applications include:

• Screening of Cathepsin B/L inhibitors

• Activity evaluation of candidate compounds

3. Trypsin-like serine protease research

Leveraging its Arg recognition properties for in-depth studies on trypsin activity, kallikrein, plasmin, and substrate specificity.

Applicable to:

• Activity analysis of trypsin, plasmin, kallikrein

• Substrate specificity and kinetics of proteases

✅ Classic substrate for Cathepsin detection, with mature literature applications

The Z-Phe-Arg sequence has long been used in Cathepsin B/L-related research, with a mature literature base. This allows researchers to directly reference classical publications for fast and stable establishment of quantitative protease activity analysis and detection methods.

✅ 4MβNA fluorescence signal, high detection sensitivity

After cleavage, the fluorescent 4MβNA product is released. Changes in the fluorescence signal reflect the degree of substrate hydrolysis, making it suitable for protease activity analysis and trace sample detection. It meets the high sensitivity requirements of applications such as high-throughput drug screening.

✅ Dual-class protease coverage, wide application range

A single substrate is compatible with both cathepsin and certain serine protease analyses, expanding its applicability across different protease enzyme systems.

✅ High purity process control, excellent batch-to-batch consistency

GeneSeqTools Bioscience & Technology strictly controls production processes and impurity residues to ensure high purity and outstanding batch-to-batch stability, guaranteeing reproducibility and reliability of data in enzyme activity analysis and high-throughput drug screening experiments.