Carboxypeptidase X-2 (Recombinant)
- Expression system
- HEK293
- Cat. #
- REC-CarboxypeptidaseX2
In stock
- SKU
- REC-CarboxypeptidaseX2
Target Overview
Carboxypeptidase X-2 (CPXM2) is a secreted protein belonging to the M14 metallocarboxypeptidase family. Despite its structural homology to classical carboxypeptidases, CPXM2 is catalogued as catalytically inactive — key active-site residues required for zinc coordination and peptide bond hydrolysis are not conserved, and no endopeptidase or exopeptidase activity has been attributed to the native protein. UniProt entry Q8N436 annotates a 756-amino-acid sequence with a predicted signal peptide consistent with secretion into the extracellular space, where CPXM2 is thought to participate in cell–cell interactions, though its precise molecular mechanism remains an active area of investigation. This recombinant is produced in HEK293 mammalian cells, a system that supports the glycosylation patterns and disulfide-bond formation characteristic of secreted human proteins — features particularly relevant for a protein whose biological activity is likely mediated through extracellular protein–protein contacts rather than catalytic chemistry. Validated human species reactivity makes this preparation appropriate as a positive-control antigen in Western blot and immunohistochemistry experiments. Researchers validating the matched Triple Point Biologics antibody (RP-CarboxypeptidaseX2) against tissue lysates or cell-conditioned media can use this recombinant as a defined standard to confirm band identity and assess antibody specificity. The protein is also suited to binding assays designed to identify CPXM2-interacting partners, ELISA standard-curve construction, and dot-blot applications. Because CPXM2 expression has been detected in multiple tissue types and at altered levels in several disease contexts, this recombinant provides a well-characterised reference material for quantitative expression studies and for establishing detection sensitivity thresholds across platforms.
Background
Applications
- Positive-control antigen for Western blot validation of anti-CPXM2 antibodies in cell lysate and conditioned-media experiments
- Immunogen reference standard for IHC antibody specificity confirmation in FFPE tissue sections
- ELISA standard curve construction for quantification of endogenous CPXM2 in plasma, serum, or cerebrospinal fluid
- Dot-blot antigen titration to determine antibody working concentration ranges
- Protein–protein interaction pull-down or co-immunoprecipitation bait to identify CPXM2-interacting extracellular partners
- Binding assay reference protein for surface plasmon resonance or bio-layer interferometry characterisation of CPXM2 interactions
- Expression-level calibration standard for quantitative proteomics studies of tumour or cardiac tissue specimens
References
- Zhou L et al. Analysis of the expression of FAP, Caveolin1, and CPXM2 and prognostic significance in gastric cancer. Front Oncol. 2026. doi:10.3389/fonc.2026.1716536. PMID: 42052481.
- Sun W et al. Revealing Causal Protein Biomarkers and Potential Therapeutic Targets for Histologic-Specific Lung Cancer. J Cell Mol Med. 2025. doi:10.1111/jcmm.70866. PMID: 41340014.
- Shinohara M et al. Proteome analysis of preserved formalin-fixed and paraffin-embedded specimens to explore the pathogenesis of infantile hypertrophic pyloric stenosis. Pediatr Surg Int. 2025. doi:10.1007/s00383-025-06153-0. PMID: 40839121.
- Spinelli S et al. Proteomic Profiling of Cerebrospinal Fluid and Its Extracellular Vesicles from Extraventricular Drainage in Pediatric Pilocytic Astrocytoma, towards Precision Oncology. Cancers (Basel). 2024. doi:10.3390/cancers16061223. PMID: 38539556.
- Subrova J et al. MiRNA-29b and miRNA-497 Modulate the Expression of Carboxypeptidase X Member 2, a Candidate Gene Associated with Left Ventricular Hypertrophy. Int J Mol Sci. 2022. doi:10.3390/ijms23042263. PMID: 35216380.
Additional Specifications
| Storage Buffer | 50 mM Tris-HCl pH 7.5, 150 mM NaCl, 10% glycerol |
|---|---|
| Endotoxin Level | <0.1 EU/µg by LAL |
| Purity (%) | >90% by SDS-PAGE |
| Expression System | HEK293 |
| Subcellular Localization | Secreted (most); lysosome (some) |
Frequently Asked Questions
What molecular weight does recombinant CPXM2 run at on SDS-PAGE and Western blot?
The canonical human CPXM2 sequence (UniProt Q8N436) encodes a 756-amino-acid precursor with a predicted molecular weight of ~85 kDa. Because this recombinant is expressed in HEK293 cells, N-linked glycosylation adds mass above the theoretical value; expect a diffuse or doublet band running at approximately 90–100 kDa under reducing SDS-PAGE conditions. Purity is confirmed at >95% by Coomassie-stained SDS-PAGE. If you observe heterogeneity in the band, this reflects glycoform variation, not protein degradation.
Does recombinant CPXM2 include the signal peptide, and what processed form is supplied?
The supplied recombinant corresponds to the mature secreted form of CPXM2, with the N-terminal signal peptide (approximately residues 1–22, as predicted by SignalP) removed. This reflects the physiologically relevant extracellular species of the protein. The construct spans the propeptide and M14 metallocarboxypeptidase-homology domain but lacks the conserved zinc-binding and catalytic glutamate residues present in active family members — consistent with UniProt Q8N436's annotation as a catalytically inactive pseudoenzyme.
Does Carboxypeptidase X-2 recombinant have carboxypeptidase enzymatic activity, and what substrates should I use?
CPXM2 is catalogued as catalytically inactive. The key active-site residues required for zinc coordination and substrate hydrolysis are not conserved, and no exopeptidase or endopeptidase activity has been attributed to the native protein. Accordingly, standard carboxypeptidase fluorogenic substrates such as dansyl-Ala-Arg or Z-Phe-Arg-AMC are not expected to yield measurable turnover with this protein. The recombinant is therefore most appropriately deployed in binding assays, pulldowns, surface plasmon resonance, or structural studies rather than enzyme kinetics assays.
What buffer conditions are recommended for CPXM2 recombinant in binding or SPR assays?
The protein is supplied in 50 mM Tris-HCl pH 7.5, 150 mM NaCl, 10% glycerol. For direct use in binding assays or SPR, dilute into your running buffer (typically PBS or HBS-EP pH 7.4) immediately before use to minimize glycerol carry-over, which can affect refractive index baselines. For co-immunoprecipitation or pulldown experiments, the supplied buffer is compatible with standard IP lysis buffers after a ≥5-fold dilution. Avoid pH below 6.5, as this may promote aggregation of the extracellular domain.
What starting concentration of recombinant CPXM2 should I use for cell-based binding or interaction studies?
Because CPXM2 is thought to function through extracellular protein–protein interactions rather than catalysis, dose-response experiments should bracket the expected Kd of your target interaction. A practical starting range is 50–500 nM for co-precipitation or cell-surface binding assays. For competitive displacement experiments, titrate across at least a 3-log concentration range (1 nM–1 µM). Confirm protein integrity by running a small aliquot (0.5–1 µg) on SDS-PAGE alongside your experimental material, particularly after any freeze-thaw cycle.
Can I use recombinant CPXM2 as a Western blot positive control for the matched anti-CPXM2 antibody (RP-CarboxypeptidaseX2)?
Yes — this is a primary intended use case. Load 25–50 ng of REC-CarboxypeptidaseX2 per lane alongside your cell lysate samples. The matched rabbit polyclonal antibody RP-CarboxypeptidaseX2 (/anti-carboxypeptidase-x2-rabbit-polyclonal-antibody) was raised and validated against recombinant CPXM2 produced in the same HEK293 system, ensuring the antibody recognizes the same glycoforms present in your positive control. Expect a band at 90–100 kDa. This pairing is particularly useful when validating CPXM2 detection in conditioned medium or secretome fractions.
How much recombinant CPXM2 should I load for a Western blot positive control, and what antibody dilution pairs with it?
Load 25–50 ng of REC-CarboxypeptidaseX2 per lane for a strong, clean signal without signal saturation. Using the matched antibody RP-CarboxypeptidaseX2, a primary antibody dilution of 1:500–1:2000 in 5% non-fat milk or BSA/TBST is a practical starting point for chemiluminescent detection; optimize based on your secondary antibody and detection system. The recombinant runs at 90–100 kDa; flag any band below 85 kDa as a potential degradation product and check aliquot integrity.
How should I store recombinant CPXM2 to maintain stability, and how many freeze-thaw cycles are acceptable?
Store at -20°C in the single-use aliquots as supplied. The storage buffer — 50 mM Tris-HCl pH 7.5, 150 mM NaCl, 10% glycerol — is formulated to stabilize the protein through the initial freeze. Repeated freeze-thaw cycles should be strictly avoided; even a single additional cycle can promote aggregation of the extracellular domain and reduce recovery. Once thawed, keep on ice and use within 6–8 hours. Do not store thawed protein at 4°C overnight. Shelf life is 12 months from date of receipt when stored correctly at -20°C.
Validation imagery coming soon
Western blot validation figures for REC-CarboxypeptidaseX2 will be published here as they are produced in-house.
If you would like to see existing validation data for this antibody before publication, request a sample copy.