Anti-Pepsin A Rabbit Polyclonal Antibody

Frequently Asked Questions

What molecular weight should I expect for Pepsin A on a Western blot?

Mature Pepsin A runs at approximately 35 kDa on reducing SDS-PAGE, representing the active enzyme after cleavage of the N-terminal propeptide. The inactive zymogen pepsinogen migrates around 40-42 kDa. In gastric mucosa lysates or cell lines expressing pepsinogen isoforms, you may detect both forms depending on sample pH and processing conditions. Samples collected at neutral pH typically show predominant pepsinogen bands, while acidic extraction can trigger autocatalytic conversion to the mature enzyme. Always include a positive control such as human gastric mucosa lysate to confirm expected band patterns.

Does this antibody distinguish between pepsinogen isoforms PGA3, PGA4, and PGA5?

This polyclonal antibody is raised against Pepsin A and recognizes epitopes shared across pepsinogen A family members, so it will likely cross-react with PGA3, PGA4, and PGA5 isoforms. Pepsinogen A isoforms share substantial sequence homology, making isoform-specific detection challenging without peptide-mapped monoclonals. If your experimental question requires discrimination between PGA5 and other gastric pepsinogens, consider complementary approaches such as isoform-specific RT-PCR or mass spectrometry. For general pepsinogen A detection in tissue lysates or to assess total gastric chief cell marker expression, cross-reactivity across isoforms is often acceptable and even advantageous.

What starting dilution should I use for Western blot with this Pepsin A antibody?

Begin at 1:1000 dilution in blocking buffer for Western blot, as recommended in our validation data. Pepsinogen and Pepsin A are abundant in gastric tissue, so this dilution typically provides strong signal without excessive background. If you are working with non-gastric samples where pepsinogen expression is lower, such as metaplastic esophageal tissue in Barrett's studies, you may need to titrate down to 1:500. Overnight incubation at 4°C often improves sensitivity compared to one-hour room-temperature binding. Always include a no-primary control and consider running a gastric mucosa lysate in parallel as a positive standard.

Can I use this rabbit polyclonal Pepsin A antibody on mouse or rat tissue?

This antibody is validated for human Pepsin A. Cross-reactivity with mouse or rat pepsinogen is predicted but not experimentally confirmed by Triple Point Biologics. Murine pepsinogens share approximately 70-80 percent sequence identity with human orthologs in conserved catalytic domains, so polyclonal sera often recognize rodent targets. If you need to probe mouse or rat gastric samples, test the antibody at the recommended 1:1000 dilution alongside a known-positive human control. Expect possible differences in band intensity or minor shifts in apparent molecular weight. For definitive rodent work, consider species-matched validation or peptide competition assays to confirm specificity.

What sample preparation is critical when working with pepsinogen to prevent autocatalytic activation?

Pepsinogen undergoes rapid autocatalytic conversion to Pepsin A at acidic pH, so maintain samples at neutral to slightly alkaline pH during lysis and storage. Use standard RIPA or similar lysis buffers at pH 7.4 with protease inhibitor cocktails, and keep samples on ice. Avoid acidic buffers or prolonged storage at room temperature, which can trigger zymogen cleavage and complicate interpretation of Western blots. If your goal is to detect only the zymogen form, work quickly and confirm lysate pH. Conversely, if studying pepsin maturation dynamics, controlled acidification can be used experimentally, but document pH conditions carefully in your methods.

What positive and negative control tissues should I use for Pepsin A immunostaining?

Human gastric mucosa is the gold-standard positive control, where chief cells in the gastric glands abundantly express pepsinogen. Fundic and body regions show strongest staining; antral mucosa has lower chief cell density. Negative controls include tissues lacking gastric-type epithelium such as liver, skeletal muscle, or normal squamous esophagus. In Barrett's esophagus studies, normal squamous mucosa serves as an internal negative control, while areas of gastric metaplasia may show aberrant pepsinogen expression. For specificity checks, pre-incubate antibody with blocking peptide if available, or omit primary antibody to assess non-specific secondary binding.

How should I store this Pepsin A 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 reduce titer and increase aggregation. Polyclonal rabbit sera are generally stable for at least two years under these conditions. Once thawed, an aliquot can be held at 4°C for up to one month; addition of 0.02-0.05 percent sodium azide helps prevent microbial growth if you prefer liquid storage. Avoid prolonged exposure to room temperature. If you notice precipitate after thawing, centrifuge briefly before use. Triple Point Biologics has manufactured proteinase antibodies since 1994, and our formulations are optimized for long-term stability without glycerol or other cryoprotectants that may interfere with downstream applications.

Will this antibody work for immunohistochemistry on formalin-fixed paraffin-embedded gastric biopsies?

Yes, Triple Point Biologics antibodies are validated for immunohistochemistry, including FFPE sections. For Pepsin A detection in gastric biopsies, perform heat-induced epitope retrieval in citrate buffer pH 6.0 or Tris-EDTA pH 9.0; citrate is a common starting point for pepsinogen immunostaining. Use the antibody at a dilution between 1:100 and 1:500, titrating based on your detection system and tissue fixation time. Overfixed samples may require longer retrieval or higher antibody concentration. Expect cytoplasmic staining in chief cells concentrated in the lower third of gastric glands. Appropriate positive and negative tissue controls are essential for interpreting staining specificity in metaplastic or neoplastic samples.