Anti-Carboxypeptidase-X2 Rabbit Polyclonal Antibody

Frequently Asked Questions

What molecular weight should I expect for CPXM2 on Western blot?

CPXM2 (Q8N436) has a predicted molecular weight of approximately 84 kDa based on its 756-residue sequence. However, because CPXM2 is a secreted glycoprotein, the apparent molecular weight on Western blot typically runs higher, often in the 90-110 kDa range depending on glycosylation state and tissue source. If you are analyzing conditioned media or serum samples, expect the fully glycosylated form. Deglycosylation with PNGase F prior to SDS-PAGE can confirm glycosylation contributions if you observe multiple bands or higher-than-predicted migration.

Does this antibody distinguish CPXM2 from other carboxypeptidase family members?

This polyclonal antibody is raised against human CPXM2 and validated for specificity against CPXM2. Given the structural homology within the metallocarboxypeptidase family, we recommend including lysates or tissues known to express related family members such as CPXM1 or classical carboxypeptidases as specificity controls. Sequence alignment shows CPXM2 has divergent regions outside the zinc-binding motif, but empirical testing with knockout or knockdown lysates provides the most definitive specificity confirmation for your experimental system. Predicted cross-reactivity with other family members has not been systematically evaluated.

What is the recommended starting dilution for Western blot with this CPXM2 antibody?

The validated dilution for Western blot is 1:1000 in blocking buffer, typically 5% non-fat milk or 3% BSA in TBST. This dilution has been optimized for detecting endogenous CPXM2 in human lysates. Start at 1:1000 and titre if needed based on signal strength and background in your specific sample type. Overnight incubation at 4°C often improves sensitivity for low-abundance targets compared to 1-hour room temperature incubation. Loading 20-40 µg total protein per lane is a reasonable starting point for tissues with moderate CPXM2 expression.

Can I use this antibody for mouse or rat samples?

This antibody is validated for human CPXM2. Cross-reactivity with mouse or rat CPXM2 is predicted based on sequence homology but has not been experimentally validated. Human and mouse CPXM2 share approximately 75-80% sequence identity. If you plan to use this antibody with mouse or rat samples, we recommend testing it alongside a positive human control and confirming the expected molecular weight. Empirical validation with known CPXM2-expressing mouse tissues or cell lines is necessary before drawing conclusions from negative or unexpected results.

Why does CPXM2 lack carboxypeptidase activity despite being in that family?

CPXM2 contains amino acid substitutions in the zinc-binding motif that is essential for metallocarboxypeptidase catalytic activity. Classical carboxypeptidases coordinate zinc via conserved histidine and glutamate residues to hydrolyze C-terminal peptide bonds, but CPXM2 has lost these critical catalytic residues through evolution. Current evidence suggests CPXM2 functions in cell-cell interactions or signaling rather than proteolysis. When interpreting experimental results, researchers should consider CPXM2 as a regulatory or structural protein, not an enzyme. This distinction is important for functional assays and pathway analysis.

What positive control tissue or cell line should I use for CPXM2 Western blot?

CPXM2 expression is tissue-specific, with detection reported in cardiovascular tissues and other contexts, though comprehensive expression atlases are still emerging. For a positive control, consider using human cell lines or tissues where CPXM2 expression has been documented in transcriptomic databases such as GTEx or Human Protein Atlas. Conditioned media from secreting cell lines may provide stronger signal than whole-cell lysates since CPXM2 is a secreted protein. If you are working with a novel tissue or cell type, running a known CPXM2-expressing sample in parallel will help confirm antibody performance.

Can this antibody be used for immunohistochemistry or immunofluorescence?

Triple Point Biologics antibodies are validated for Western blot and generally suitable for IHC and immunofluorescence applications, though specific validation for this CPXM2 antibody in IHC has been performed. For IHC, antigen retrieval is typically required; citrate buffer (pH 6.0) heat-induced epitope retrieval is a reasonable starting method. Because CPXM2 is secreted, expect extracellular or pericellular staining patterns rather than intracellular localization in most tissues. Optimal dilutions for IHC are typically 5-10 times more concentrated than Western blot dilutions; start around 1:100 to 1:200 and optimize.

How should I store this antibody and what is the expected shelf life?

Store the antibody at -20°C in single-use aliquots to avoid repeated freeze-thaw cycles, which can reduce antibody activity over time. The antibody is supplied at 100 µg in a glycerol-containing buffer that remains liquid at -20°C, allowing direct pipetting without thawing if stored properly. For long-term storage beyond one year, -80°C is preferable. Once thawed, aliquots can be stored at 4°C for up to one month with sodium azide preservative. Avoid storing diluted antibody; prepare working dilutions fresh for each experiment to maintain optimal performance.