PRSS-42 (Recombinant)

Frequently Asked Questions

What is the expected molecular weight of recombinant PRSS-42 on SDS-PAGE or Western blot?

The full-length PRSS-42 construct spans all 293 residues, giving a predicted molecular weight of approximately 32–33 kDa. On reducing SDS-PAGE, the recombinant typically migrates at 34–37 kDa due to glycosylation added during HEK293 expression. If you are running a non-reducing gel, expect a similar single band — no disulfide-linked dimers have been observed under standard conditions. Purity is >95% by SDS-PAGE, so the preparation is clean enough to use directly as a size reference without further fractionation.

Is PRSS-42 a catalytically active serine protease or a pseudogene-derived non-functional protein?

This is the central question in the field. In humans, PRSS42P is annotated as a pseudogene-derived locus (UniProt Q7Z5A4), and canonical catalytic triad integrity is debated. Mouse functional orthologues (Tessp-2) have demonstrated protease activity in spermatogenesis. This recombinant is expressed in HEK293 cells from the full 293-residue human sequence and is supplied as an active enzyme preparation under EC 3.4.21.- classification, but researchers should validate activity independently using fluorogenic substrates (see activity assay FAQ below) given the unresolved status of the human protein.

What fluorogenic substrate should I use to assay PRSS-42 serine protease activity in vitro?

For initial activity screening, Boc-Val-Pro-Arg-AMC or Z-Phe-Arg-AMC (both broad trypsin-like serine protease substrates) are reasonable starting points given PRSS-42's classification under EC 3.4.21.-. Run assays in 50 mM Tris-HCl pH 7.5, 150 mM NaCl (matching the storage buffer) to avoid buffer-exchange artifacts. Include 1 mM PMSF or 100 µM AEBSF as serine protease inhibitor controls. Because human PRSS-42 activity remains unconfirmed in the literature, a no-enzyme blank and a confirmed serine protease (e.g., trypsin) positive control should be run in parallel to validate assay sensitivity.

What starting concentration and buffer conditions are recommended for a PRSS-42 activity assay?

Start at 0.5–2 µg recombinant PRSS-42 per 100 µL reaction in 50 mM Tris-HCl pH 7.5, 150 mM NaCl — this directly matches the storage buffer, avoiding any dilution-induced precipitation. Substrate concentrations of 50–200 µM AMC-conjugated peptide cover the typical Km range for trypsin-like serine proteases. Incubate at 37°C and read fluorescence (Ex/Em 380/460 nm) at 5-minute intervals over 60 minutes. If signal is low, titrate enzyme up to 5 µg; PRSS-42's activity level in the human form may be modest relative to classical serine proteases.

Can I use recombinant PRSS-42 as a positive control antigen for Western blot with the matched TPB antibody RP-PRSS42?

Yes — that is one of the primary validated uses of this recombinant. The matched rabbit polyclonal antibody RP-PRSS42 (/anti-prss-42-rabbit-polyclonal-antibody) was raised and validated in the same laboratory using this recombinant as immunogen, so antigen-antibody compatibility is confirmed for Western blot. Load 20–50 ng of recombinant PRSS-42 per lane on a standard 12% SDS-PAGE gel; at 50 ng you should resolve a clean band at ~34–37 kDa with RP-PRSS42 at 1:500–1:2000 dilution. This lane serves as a reliable reference when blotting tissue lysates of uncertain expression level.

How much recombinant PRSS-42 should I load for a Western blot positive control lane?

20–50 ng per lane is the practical working range. At 20 ng, the band is detectable with RP-PRSS42 (1:1000) using HRP-conjugated secondary antibody and standard ECL — suitable when minimizing antigen consumption across multiple experiments. At 50 ng, the band is robust enough to serve as a visual reference even on overexposed films. Avoid loading above 100 ng; signal saturation and cross-lane bleed can obscure adjacent sample lanes. Because purity exceeds 95%, no background bands from host-cell contamination are expected at these concentrations.

Does recombinant PRSS-42 from HEK293 cells carry post-translational modifications relevant to native testis protein?

HEK293 expression supports N-linked glycosylation and other mammalian post-translational modifications, which is why this system was chosen over bacterial expression for a testis-expressed protein like PRSS-42. The slight upward shift on SDS-PAGE (predicted ~32–33 kDa, observed ~34–37 kDa) is consistent with glycosylation. Whether the specific glycan pattern matches native testicular PRSS-42 has not been independently confirmed; if glycan identity is critical to your study, PNGase F digestion of the recombinant followed by mass spectrometry is advisable before drawing structural conclusions.

How should I store and handle recombinant PRSS-42 to maintain activity and avoid degradation?

Store at -20°C in single-use aliquots immediately upon receipt. The storage buffer — 50 mM Tris-HCl pH 7.5, 150 mM NaCl, 10% glycerol — stabilises the protein through freeze-thaw, but repeated cycling will reduce activity and promote aggregation; plan aliquot sizes around a single experiment's needs. On the bench, keep the protein on ice and use within 4 hours of thawing. Do not dilute into water or low-salt buffers; maintain ionic strength to prevent precipitation. Shelf life at -20°C is 12 months from date of receipt when stored correctly. Avoid storage at -80°C for routine use as repeated retrieval increases freeze-thaw risk.