FabULOUS SpeB SmartEnzymes™ loga



FabULOUS (SpeB) is a recombinantly produced cysteine protease that under reduced conditions digests in the hinge region of antibodies from many species and subclasses, including human, mouse, rat and goat.


FabULOUS is available in two product formats:

  • FabULOUS Enzyme - lyophilized enzyme
  • FabULOUS Fab kit - lyophilized enzyme and affinity purification resin for easy generation and purification of Fab fragments from mouse IgG.

Product Information

FabULOUS (SpeB) is an enzyme for digestion of IgG in the hinge region. Human, mouse, rat, goat and sheep IgG are digested by FabULOUS, yielding Fab and Fc fragments. The primary digestion site on human IgG1 is ..KTHT / CPPCPAPE...

FabULOUS is derived from Streptococcus pyogenes and is expressed in E. coli. The molecular weight of FabULOUS is 29 kDa and the enzyme contains a His-tag.

Key Characteristics

  • Human IgG1-4, IgG from mouse, rat, goat, sheep and rabbit
  • 60 min reaction
  • Requires reducing conditions
  • Human IgG1: KTHT / CPPCPAP (above the hinge)


Purified and homogenous Fab fragments can be used in many applications, including:

  • Study monovalent binding of Fab fragments to the antigen
  • Elimination of Fc-mediated effector functions
  • Reduced unspecific binding from Fc interactions

Product Formats

FabULOUS Enzyme

FabULOUS enzyme supplied as lyophilized powder. The enzyme is available in a 2000 unit vial (1 unit digests 1 ug IgG).

FabULOUS Fab kit mouse

FabULOUS Fab kit mouse is used for rapid and easy preparation and purification of Fab fragments from mouse IgG. The kit consists of two parts; lyophilized FabULOUS enzyme and affinity spin columns for purification of intact Fab fragments.

FabULOUS Brochures, Posters and Applications

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Brochures and Posters

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FabULOUS SmartEnzyme Reference Tool

SmartEnzyme Reference Tool

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FabULOUS Applications


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Download FabULOUS Poster and External References

FabULOUS SpeB Antibody Characterization Poster

CASSS 2013

"Initial Characterization of a Recombinantly Modified SpeB from S. pyogenes for Antibody Subunit Domain Generation"

FabULOUS SpeB references


Find external articles and papers using FabULOUS



FAQ and Support

Popular FAQ

Yes, FabULOUS should be able to digest a Fc fusion protein as long as you have not fused the protein too close to the cleavage site. FabULOUS digests human IgG1 just above the hinge (…KTHT / CPPCP…).

Depending on what reducing agent and what concentration you use you can obtain intact Fab and not reduce the interchain disulfide bond. The light chain (LC) and heavy chain (HC) will not dissociate under native conditions due to hydrogen/hydrophobic forces. Before you analyze your samples with SDS-PAGE you must remove the cysteine otherwise the Fab will be reduced to Fd and LC during sample preparation for the SDS-PAGE. This can be done by a simple buffer exchange.

Yes. There is the possibility to exchange the CaptureSelect LC-kappa (mur) columns to columns containing CaptureSelect LC-lambda (mouse). This resin is specific for mouse IgG. Please contact support@genovis.com if this is of interest.

FabULOUS is a cysteine protease that digests IgG in the hinge region. A primary digestion site for human IgG1 is above the hinge (…KTHT / CPPCP…). The enzyme is also active on human IgG2 and IgG3, digestion site not determined but Fab and Fc is generated. FabULOUS digests human IgG4 primarily at a site below the hinge using significantly longer incubation, generating Fab’ due to the reducing conditions. The possibility of other, secondary digestions sites is antibody dependent

No, FabULOUS Fab kit contains CaptureSelect LC-kappa (mur) spin columns with selective affinity for murine LC-kappa. If you need to generate pure Fab from human IgG1 you can use either FabALACTICA Fab Kit or GingisKHAN Fab Kit. If you have a different subclass of human IgG, please contact support@genovis.com for guidance.


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