Anti-Carboxypeptidase X1 (CPXM1) Rabbit Polyclonal Antibody

Frequently Asked Questions

What molecular weight band should I expect for CPXM1 on Western blot?

CPXM1 has a predicted molecular weight of approximately 82 kDa based on its 734-residue sequence. However, because CPXM1 is a secreted glycoprotein with potential post-translational modifications, the observed band may migrate at a higher apparent molecular weight, often between 85-95 kDa depending on glycosylation status and the cell type. If you are analyzing conditioned media or extracellular fractions, expect a mature processed form. In whole-cell lysates from cells with low secretion efficiency, you may also detect intracellular precursor forms. Running a positive control lysate from CPXM1-expressing cells will help confirm the expected migration pattern in your system.

Does CPXM1 have catalytic carboxypeptidase activity I need to account for in my assay?

No carboxypeptidase activity has been experimentally demonstrated for CPXM1 despite its classification in the M14 metallocarboxypeptidase family. Current evidence suggests CPXM1 functions primarily in cell-cell interactions or adhesion rather than peptide cleavage. This means you should not expect substrate cleavage in standard carboxypeptidase activity assays. If your experimental design assumes enzymatic activity, consider that CPXM1 may instead be participating in protein-protein interactions or acting as a structural component. This functional distinction is important when interpreting co-immunoprecipitation or binding studies where CPXM1 is present.

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

The validated dilution for Western blot is 1:1000 in blocking buffer. This dilution has been tested with human samples and provides a good starting point for most standard protocols. Optimal dilution may vary depending on CPXM1 expression level in your sample, membrane type, detection method, and blocking conditions. For samples with low CPXM1 expression, you may need to increase antibody concentration to 1:500. Conversely, if you observe high background, diluting to 1:2000 can improve signal-to-noise ratio. We recommend titrating the antibody with your specific lysate and detection system to determine the optimal working dilution for your application.

Which sample types are best for detecting CPXM1 with this antibody?

Because CPXM1 is a secreted protein, conditioned culture media from CPXM1-expressing cells often yields the strongest signal with less background than whole-cell lysates. Concentrate conditioned media 10- to 20-fold using centrifugal filters before loading to improve detection. For tissue samples, CPXM1 should be present in extracellular matrix fractions. If working with cell lysates, include both cytoplasmic and membrane fractions, as intracellular precursor forms may be retained in the secretory pathway. Avoid prolonged sample storage at 4°C, as secreted metallocarboxypeptidases can be susceptible to proteolytic cleavage. Flash-freeze samples and store at -80°C until analysis.

Will this antibody cross-react with other carboxypeptidase family members?

This antibody has been validated specifically for human CPXM1. The M14 carboxypeptidase family includes numerous members with conserved metallocarboxypeptidase domains, so cross-reactivity with closely related proteins such as CPXM2 is possible but has not been systematically tested. If you are working in a system expressing multiple carboxypeptidase family members, consider running parallel experiments with siRNA knockdown or CRISPR knockout of CPXM1 to confirm band identity. Alternatively, immunoprecipitation followed by mass spectrometry can definitively identify which carboxypeptidase proteins are recognized. For applications requiring absolute specificity, validate the antibody in your experimental context with appropriate negative controls.

Does this antibody work in mouse or rat samples?

This antibody has been validated only for human CPXM1. Cross-reactivity with mouse or rat orthologs is predicted based on sequence homology but has not been experimentally confirmed. Human CPXM1 shares approximately 80-85% identity with rodent orthologs, with conservation higher in the catalytic domain than in the propeptide region. If you need to detect CPXM1 in rodent samples, test the antibody at the recommended 1:1000 dilution initially, but be prepared to optimize or use a species-specific antibody if results are inconclusive. Include a human positive control lysate on the same blot to confirm antibody function and compare band migration patterns.

Can I use this antibody for immunohistochemistry or immunofluorescence?

Triple Point Biologics antibodies are routinely validated for Western blot applications. This rabbit polyclonal antibody should be compatible with immunohistochemistry and immunofluorescence protocols, though optimal dilutions and antigen retrieval conditions will need to be determined empirically for your tissue type. For IHC, start with a 1:100 to 1:200 dilution and test antigen retrieval methods such as citrate buffer pH 6.0 or Tris-EDTA pH 9.0. Because CPXM1 is secreted, expect extracellular or pericellular staining patterns rather than intracellular localization. Include appropriate positive control tissues known to express CPXM1 based on RNA expression databases.

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

Store the antibody at -20°C in small aliquots to avoid repeated freeze-thaw cycles, which can compromise antibody stability and performance. Once thawed, an aliquot can be kept at 4°C for up to one month if sodium azide preservative is present, but long-term storage should always be frozen. Do not store diluted antibody; prepare working dilutions fresh for each experiment. The lyophilized or stock formulation is stable for at least one year from the date of manufacture when stored properly at -20°C. If you observe decreased signal intensity or increased background over time, the antibody may have degraded and a fresh aliquot should be used.