MMP-21 (Recombinant)

Frequently Asked Questions

What molecular weight band should I expect for recombinant MMP-21 on SDS-PAGE or Western blot?

The full-length human MMP-21 sequence is 569 amino acids, giving a predicted unglycosylated molecular weight of approximately 63 kDa. Because this recombinant is produced in HEK293 cells, N-linked glycosylation adds heterogeneous mass, so the observed band on reducing SDS-PAGE typically runs at 70–80 kDa. Under non-reducing conditions, expect a similar position unless disulfide-linked dimers are present. When using our matched antibody RP-MMP21 for Western blot, a band in the 70–80 kDa range serves as the expected positive control signal.

What processing or activation state is this recombinant MMP-21 supplied in — zymogen or active form?

REC-MMP21 is supplied as the active enzyme form; the propeptide cysteine-switch has been removed during processing, exposing the functional catalytic domain. It is not a zymogen requiring exogenous activation with APMA. The catalytic domain retains the conserved HEXXHXXGXXH zinc-binding motif characteristic of MMP family members. If your assay design requires a latent zymogen as a control, this product is not appropriate for that purpose — it is intended for direct functional and binding experiments.

What substrate should I use to measure MMP-21 proteolytic activity in a fluorogenic assay?

The best-characterised natural substrate for MMP-21 is alpha-1-antitrypsin. For fluorogenic assays, a generic broad-spectrum MMP substrate such as Mca-PLGL-Dpa-AR-NH2 (Knight substrate) is commonly used and is cleaved by MMP-21 in vitro. Alpha-1-antitrypsin-derived peptides can also be used for native cleavage assays resolved by SDS-PAGE. Assay buffer should match REC-MMP21's storage buffer — 50 mM Tris-HCl pH 7.5, 150 mM NaCl, 5 mM CaCl2 — to maintain zinc-dependent catalytic activity. Include 0.05% Brij-35 to prevent nonspecific surface adsorption at low enzyme concentrations.

What starting concentration of recombinant MMP-21 should I use in an activity assay?

A practical starting point is 1–10 nM REC-MMP21 in the assay well for fluorogenic substrate experiments, with substrate concentrations ranging from 5–50 µM to bracket the expected Km. For cleavage assays with native alpha-1-antitrypsin resolved by SDS-PAGE, 100–500 ng of enzyme per reaction is a reasonable starting range at a 1:10 to 1:50 enzyme-to-substrate molar ratio. Titrate enzyme concentration empirically, as specific activity can vary with lot. Always include a no-enzyme blank and a metalloproteinase inhibitor control (e.g., 10 mM EDTA or 1 µM marimastat) to confirm zinc-dependent activity.

How does calcium in the storage buffer affect MMP-21 activity assay buffer design?

REC-MMP21 is stored in 50 mM Tris-HCl pH 7.5, 150 mM NaCl, 10% glycerol, 5 mM CaCl2. The calcium is essential for MMP catalytic domain stability — do not use EGTA or EDTA-containing buffers, as chelation will inhibit the enzyme. When diluting into assay buffer, maintain at least 1–5 mM CaCl2 in the final assay volume. Glycerol dilution from the stock is generally tolerable at ≤1% in the final reaction. Zinc supplementation (1–10 µM ZnCl2) can be added if activity appears lower than expected after dilution.

Can I use REC-MMP21 as a positive control for Western blot with the RP-MMP21 antibody?

Yes — REC-MMP21 and RP-MMP21 are produced as a matched pair specifically for this purpose. Load 20–50 ng of REC-MMP21 per lane on a 10% or 12% SDS-PAGE gel under reducing conditions. After transfer and blocking, RP-MMP21 should detect the recombinant at 70–80 kDa (HEK293-glycosylated form). This loading range gives a clean, non-saturated band that can be used alongside cell lysate lanes to confirm antibody performance. The antibody has been validated against this recombinant in-house, so band identity is not ambiguous.

How much recombinant MMP-21 should I load for a Western blot positive control lane alongside tissue lysates?

Load 25–50 ng of REC-MMP21 per lane. At this amount, RP-MMP21 (used at a 1:1000–1:2000 primary antibody dilution) produces a robust signal at 70–80 kDa on standard PVDF or nitrocellulose membranes with HRP-conjugated secondary antibodies and ECL detection. Loading more than 100 ng risks signal bleed into adjacent sample lanes. If your tissue lysate is from a MMP-21-low source, reducing the recombinant load to 10–20 ng helps avoid a disproportionately dominant positive control band that obscures relative quantitation.

What is the best way to store and handle REC-MMP21 to avoid loss of activity after receipt?

Upon receipt, centrifuge briefly to collect liquid, then aliquot immediately into single-use volumes appropriate for your typical experiment — avoid working from a master tube repeatedly. Store at -20°C; the 10% glycerol in the buffer (50 mM Tris-HCl pH 7.5, 150 mM NaCl, 5 mM CaCl2) provides cryoprotection without requiring -80°C. Shelf life at -20°C in unopened aliquots is 12 months from date of manufacture. For working dilutions, prepare fresh in assay buffer on ice and use within 4 hours; dilute protein below 10 µg/mL can adsorb to tube walls — adding 0.1% BSA (protease-free) to dilution buffer mitigates this.