Choosing the right IVT enzymes for mRNA manufacturing sets the quality of the drug substance, a single, interoperable GMP-grade, low-dsRNA enzyme suite spanning all five stages of the mRNA workflow, from in vitro transcription to a purified drug substance.
Why IVT enzymes decide mRNA quality
The performance of an mRNA drug substance is largely set at the bench, by the enzymes used to make it. Yield, capping efficiency, poly(A) tail integrity, residual template DNA, host-cell nucleic-acid carryover, and, most critically, the level of double-stranded RNA (dsRNA) byproduct are all direct consequences of the IVT enzymes in the reaction.
dsRNA is the dominant driver of innate-immune activation against synthetic mRNA, and removing it is directly linked to lower immunogenicity and higher translation.1,2 Wild-type T7 RNA polymerase generates dsRNA through self-templated 3′-end extension and RNA-dependent side activities, so even a trace of byproduct can trigger interferon responses that blunt translation and raise reactogenicity.3 Downstream, residual DNA template and host-cell DNA/RNA must be cleared to pg-level to meet regulatory and safety expectations.
The suite below, assembled from BioHippo's molecular-enzymes catalog, addresses each of these failure points across five workflow stages, with GMP-grade and animal-origin-free options suitable for process development through commercial manufacturing.
Five enzymatic stages, one integrated toolbox
The suite is designed to be operated as one continuous workflow rather than a set of mismatched reagents, all enzymes share compatible buffers and 37 °C reaction optima.
Transcription. A linearized DNA template is transcribed into RNA. Low-dsRNA T7 RNA Polymerase drives high-yield synthesis while suppressing dsRNA; inorganic pyrophosphatase hydrolyzes pyrophosphate to push the reaction forward and maximize yield.
5′ Capping. A functional cap is installed co-transcriptionally (cap analog) or enzymatically with Vaccinia Capping Enzyme (Cap 0), then converted to the immune-evasive Cap 1 by mRNA Cap 2′-O-Methyltransferase.
3′ Poly(A) tailing. Where the tail is not template-encoded, E. coli Poly(A) Polymerase adds a template-independent poly(A) tail to stabilize the transcript and support translation.
Template removal. RNase-free DNase I digests the DNA template after transcription, delivering DNA-free RNA ahead of purification.
Clearance & carryover control. Salt Active UltraNuclease reduces host and process nucleic acids to pg-grade during purification; heat-labile UDG controls dU carryover in any coupled amplification/QC steps.
Stage 1 · Transcription: high-yield T7 RNA polymerase with dsRNA suppression
The choice of T7 RNA polymerase is the single most consequential decision in the whole workflow, because it sets both yield and the dsRNA burden that everything downstream must contend with.
Core enzyme · engineered low-dsRNA variant · recommended
Hieff™ T7 RNA Polymerase (GMP-grade, low dsRNA, 250 U/µL)
An engineered T7 RNA polymerase variant that delivers IVT yields comparable to wild type while suppressing dsRNA formation to roughly 1/100,000 of wild-type levels, by lowering the terminal-transferase and RNA-dependent RNA polymerase side activities responsible for dsRNA. It efficiently incorporates cap analogs and is compatible with CleanCap® AG and LZCap for one-step co-transcriptional capping.
- dsRNA ↓ ~10⁵-fold vs. WT
- Capping efficiency >99%
- mRNA integrity >90%
- Purity ≥95%
- Endotoxin <20 EU/mg
- Host DNA <10 fg/U
- Animal-origin-free
In murine RAW264.7 macrophages, mRNA transcribed with this variant induced markedly lower IFN-β mRNA and protein than wild-type-transcribed mRNA, direct evidence of reduced immunogenicity. The mechanism is described in a peer-reviewed study (The FEBS Journal, 2025).
Two alternative T7 polymerases
CleaScrip™ T7 RNA Polymerase (low dsRNA) offers the same dsRNA-suppressing chemistry at research/process-development grade for construct screening; the standard T7 RNA Polymerase GMP-grade suits high-yield IVT where an engineered low-dsRNA variant is not required (e.g. saRNA with separate dsRNA polishing).
Yield-enhancing cofactor enzyme · GMP
Pyrophosphatase, Inorganic GMP-grade (1 U/µL)
Hydrolyzes the inorganic pyrophosphate released during transcription into orthophosphate, pulling the thermodynamically unfavorable polymerization forward and preventing magnesium-pyrophosphate precipitation. Adding pyrophosphatase increases RNA yield in IVT reactions; it is tested free of endonucleases, exonucleases, and RNases.
The science: why these two enzymes share one tube
The polymerase binds the T7 promoter and adds NTPs 5′→3′, releasing one pyrophosphate (PPi) per base. Because polymerization is reversible, accumulating PPi drives it backward and precipitates Mg²⁺ as magnesium pyrophosphate, starving the enzyme of its Mg²⁺ cofactor. Pyrophosphatase clears PPi to orthophosphate in the same reaction, pulling the equilibrium forward and freeing Mg²⁺. The engineered polymerase additionally lowers the terminal-transferase and RNA-dependent side activities that generate immunostimulatory dsRNA.
Stage 2 · 5′ Capping: building a Cap 1 structure for stability and immune evasion
Capping can be performed co-transcriptionally with a cap analog during Stage 1, or enzymatically after transcription using the two enzymes below. The enzymatic route is preferred when maximum, uniform capping is required, and it produces the Cap 1 structure characteristic of mammalian mRNA and central to evading cytosolic innate-immune sensors.
Cap 0 installation · GMP
mRNA Vaccinia Capping Enzyme GMP-grade (10 U/µL)
A recombinant vaccinia-virus capping enzyme (D1/D12 subunits) carrying RNA triphosphatase, guanylyltransferase, and guanine-N7-methyltransferase activities. In the presence of GTP and SAM it installs the m7Gppp (Cap 0) structure on the 5′ end of the transcript, reaching near-100% capping efficiency by mass-spectrometry analysis.
- Capping ≈100%
- No endo/exo/RNase
- Recombinant, AOF
Cap 0 → Cap 1 conversion · GMP
mRNA Cap 2′-O-Methyltransferase GMP-grade (50 U/µL)
Uses SAM as a methyl donor to add a methyl group at the 2′-O position of the first cap nucleotide, converting Cap 0 to Cap 1. The Cap 1 structure helps the transcript evade innate immune recognition in vivo and improves translation and expression after transfection.
Co-transcriptional alternative
The T7 High Yield RNA Synthesis Kit for Co-transcription (low dsRNA, with Cap1 analog) bundles low-dsRNA transcription and Cap 1 installation in a single reaction.
Stage 3 · 3′ Poly(A) tailing: template-independent poly(A) addition
3′ tail synthesis
E. coli Poly(A) Polymerase
Catalyzes template-independent addition of AMP (from ATP) to the 3′ end of single-stranded RNA, forming the poly(A) tail that stabilizes mRNA and supports efficient translation. Useful when the poly(A) tail is not encoded in the DNA template or requires extension. Supplied free of residual nuclease and RNase activity. It is selective for ATP (CTP/UTP incorporate <5%, GTP not at all), giving clean homopolymeric tails.
Stage 4 · Template removal: clearing the DNA template after transcription
Template digestion · GMP
Recombinant DNase I (RNase-free) GMP-grade (2 U/µL)
A recombinant, RNase-free endonuclease that digests single- and double-stranded DNA to short oligonucleotides, removing the DNA template after IVT and delivering DNA-free RNA. In head-to-head testing, this DNase I effectively removed template DNA during transcription relative to competitor enzymes, and it is produced under GMP with a documented specification.
- RNase-free
- Recombinant
- GMP · MSDS/manual available
The science
The DNA template is a process-related impurity, residual DNA is both a regulated safety limit and a potential innate-immune trigger. DNase I hydrolyzes phosphodiester bonds in single- and double-stranded DNA down to short oligonucleotides that partition away during purification. Because it is RNase-free, it clears the template without nicking the RNA product.
Stage 5 · Clearance & carryover control: reducing host nucleic acids to pg-grade
Downstream nucleic-acid clearance · DMF filed
Salt Active UltraNuclease GMP-grade
A nonspecific endonuclease optimized for high-salt conditions, maintaining maximum activity at 500 mM salt, where released DNA and RNA are most accessible and protein/particle aggregation is minimized. It reduces host nucleic-acid residues to pg-grade and, in AAV production case data, delivered lower host-cell DNA residuals than a leading competitor, improving purity and safety of the drug substance.
- Active to 500 mM salt
- Purity ≥99%
- Endotoxin <0.25 EU/1000 U
- Host protein <10 ppm
- DMF MF037815 · AOF
General endonuclease for clarification · GMP
UCF.ME™ UltraNuclease GMP-grade (250 U/µL)
A GMP-grade nonspecific endonuclease for reducing lysate/supernatant viscosity and removing host nucleic acids under standard-salt conditions, the general-purpose counterpart to the salt-active variant for clarification and polishing steps.
dU carryover / contamination control · ultra-low residual
UCF.ME™ Uracil DNA Glycosylase (UDG/UNG), heat-labile (1 U/µL)
An ultra-low-residual, heat-labile UDG from psychrophilic marine bacteria for any dU-based amplification or QC step coupled to the workflow. It digests dU-containing carryover to prevent false positives, then inactivates completely (e.g. 50 °C/10 min) so it cannot degrade legitimate product. E. coli genomic-DNA residue is <0.1 copies/U with no residual exonuclease, nicking, or RNase activity.
- E. coli DNA <0.1 copies/U
- Purity ≥95%
- Fully heat-labile
Manufacturing-ready specifications
The suite is built for the transition from research to regulated manufacturing: GMP-grade production, animal-origin-free options, tight impurity specifications, and regulatory support documentation.
| Attribute | Representative specification | Why it matters for mRNA |
|---|---|---|
| dsRNA suppression | ~10⁵-fold lower than WT T7 RNAP | Reduces interferon response and reactogenicity |
| Capping efficiency | >99% (low-dsRNA T7) · ≈100% (Vaccinia enzyme) | Stability, translation, immune evasion (Cap 1) |
| Endotoxin | <20 EU/mg (T7) · <0.25 EU/1000 U (UltraNuclease) | Patient safety in injectable products |
| Host-cell DNA | <10 fg/U (T7 RNAP) | Limits process-related DNA carryover |
| Nucleic-acid clearance | Host residues reduced to pg-grade | Meets residual-DNA/RNA safety limits |
| Sourcing | Animal-origin-free (AOF) options | Simplifies regulatory filing & supply |
| Regulatory support | DMF filed for Salt Active UltraNuclease (MF037815); MSDS/manuals available | Accelerates BLA/IND referencing |
Discuss this enzyme suite with a specialist
Every enzyme in this workflow is available from BioHippo with the specifications and regulatory documentation manufacturing teams need, grade selection, pack sizes, bulk and GMP supply, lead times, and documentation packages (CoA, MSDS, DMF referencing).
Talk to a specialistThe IVT enzymes for mRNA manufacturing at a glance
| Workflow stage | Product | Grade |
|---|---|---|
| Transcription | Hieff™ T7 RNA Polymerase (low dsRNA, 250 U/µL), engineered low-dsRNA variant, recommended | GMP |
| Transcription | Pyrophosphatase, Inorganic (1 U/µL), yield enhancement | GMP |
| Capping | mRNA Vaccinia Capping Enzyme (10 U/µL), Cap 0 installation | GMP |
| Capping | mRNA Cap 2′-O-Methyltransferase (50 U/µL), Cap 0 → Cap 1 | GMP |
| Tailing | E. coli Poly(A) Polymerase, template-independent poly(A) | RUO |
| Template removal | Recombinant DNase I (RNase-free, 2 U/µL), DNA template digestion | GMP |
| Clearance | Salt Active UltraNuclease, high-salt clearance · DMF MF037815 | GMP |
| Clearance | UCF.ME™ UltraNuclease (250 U/µL), general clarification / polishing | GMP |
| Carryover control | UCF.ME™ UDG (heat-labile, 1 U/µL), dU carryover prevention | RUO |
| All-in-one (alt.) | T7 High Yield RNA Synthesis Kit for Co-transcription (low dsRNA, Cap1 analog), transcription + co-transcriptional Cap 1 | Kit |
Grade designations are indicative; confirm current grade, pack size, and documentation on each product page. Browse the full molecular-enzymes range.
Frequently asked questions
What are IVT enzymes, and which do I need for mRNA manufacturing?
IVT (in vitro transcription) enzymes are the biocatalysts that build an mRNA drug substance: a T7 RNA polymerase to transcribe RNA from a DNA template, inorganic pyrophosphatase to maximize yield, capping enzymes for the 5′ cap, poly(A) polymerase for the 3′ tail, DNase I to remove the template, and nucleases to clear host nucleic acids. The minimum functional reaction is a T7 polymerase (plus pyrophosphatase) and a template-removal DNase I; capping, tailing, and clearance enzymes are added according to your construct and purity requirements.
What's the difference between GMP-grade and RUO IVT enzymes, and which do I need?
GMP-grade enzymes are manufactured under quality-controlled processes with tight impurity specifications and supporting documentation, intended for clinical and commercial mRNA production. RUO (Research Use Only) enzymes suit discovery, construct screening, and early process development. A common path is to prototype with RUO material, for example the low-dsRNA CleaScrip™ polymerase, then switch to the GMP-grade equivalent for scale-up, keeping the same underlying chemistry so results transfer.
How does the low-dsRNA T7 polymerase actually reduce immunogenicity?
Wild-type T7 RNA polymerase generates double-stranded RNA byproducts through terminal-transferase and RNA-dependent side activities, and dsRNA is the main trigger of innate-immune sensing against synthetic mRNA. The engineered Hieff™ variant lowers those side activities, cutting dsRNA to roughly 1/100,000 of wild-type levels while maintaining yield, and mRNA made with it induced markedly lower IFN-β in macrophage assays.
Do I have to use two capping enzymes, or can I cap co-transcriptionally?
Both routes work. The enzymatic route (Vaccinia Capping Enzyme for Cap 0, then Cap 2′-O-Methyltransferase for Cap 1) gives high, uniform capping in a defined post-transcription step. Alternatively, a cap analog can be incorporated during transcription for a single-reaction workflow, the low-dsRNA polymerase is compatible with cap analogs such as CleanCap® AG. Which is better depends on your scale, cost target, and capping-uniformity requirements.
What's the difference between Salt Active UltraNuclease and standard UltraNuclease?
Both are nonspecific endonucleases that clear residual host and process nucleic acids. The salt-active version keeps optimal activity at high salt (up to ~500 mM), where nucleic acids dissociate from proteins and viral capsids and are more accessible, useful in downstream purification and viral-vector processes, where it also reduces particle aggregation. The standard UltraNuclease is the general-purpose choice for viscosity reduction and clearance under normal-salt conditions.
Are the enzymes animal-origin-free, and do you provide regulatory documentation?
The suite includes animal-origin-free (AOF) options, and the GMP-grade enzymes carry tight endotoxin, host-protein, and host-DNA specifications. Documentation such as CoA and MSDS is available per product, and the Salt Active UltraNuclease has a filed Drug Master File (DMF MF037815) to support regulatory referencing. Ask a specialist for the documentation package your filing requires.
Can I get bulk or custom pack sizes for manufacturing scale?
Yes. These enzymes are available in pack sizes ranging from research quantities up to bulk manufacturing volumes (for example, litre-scale fills of the GMP capping and nuclease enzymes). For scale-up pricing, lead times, and custom formats, talk to a specialist.
References
- Karikó K, Muramatsu H, Ludwig J, Weissman D. Generating the optimal mRNA for therapy: HPLC purification eliminates immune activation and improves translation of nucleoside-modified, protein-encoding mRNA. Nucleic Acids Res. 2011;39(21):e142. PMID: 21890902. doi:10.1093/nar/gkr695
- Nelson J, Sorensen EW, Mintri S, et al. Impact of mRNA chemistry and manufacturing process on innate immune activation. Sci Adv. 2020;6(26):eaaz6893. PMID: 32637598. doi:10.1126/sciadv.aaz6893
- Gholamalipour Y, Karunanayake Mudiyanselage A, Martin CT. 3′ end additions by T7 RNA polymerase are RNA self-templated, distributive and diverse in character-RNA-Seq analyses. Nucleic Acids Res. 2018;46(18):9253–9263. PMID: 30219859. doi:10.1093/nar/gky796
Product specifications, performance data, and publications referenced in this note are drawn from the manufacturer product documentation available on each linked product page. For Research Use Only (RUO) and GMP-grade designations, verify the current status and intended-use statement on the product page before purchase. Peer-reviewed mechanism reference for the low-dsRNA T7 RNA polymerase: The FEBS Journal, 2025. BioHippo is a curated life-science marketplace offering quality-evaluated products sourced across multiple upstream suppliers.
