FabULOUS Enzyme

The FabULOUS enzyme is supplied as a lyophilized powder with no preservatives added, and is available in 2000 unit vials for digestion of up to 2 mg IgG.

FabULOUS (SpeB) is a unique recombinantly produced cysteine protease that digests antibodies from many species and subclasses in the hinge region, producing a homogenous pool of Fab fragments. The enzyme requires reducing conditions for activity on IgG.

Detailed 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...

A digestion protocol at 37°C for one hour under reducing conditions is generally applicable. FabULOUS digests IgG in commonly used buffers with pH ranging from 6.5 to 8.0. FabULOUS requires a reducing agent in the digestion reaction and the reducing agent is likely to reduce interchain thiols.

The molecular weight of FabULOUS is 29 kDa and the enzyme contains a His-tag.

Storage and Stability

The FabULOUS enzyme is supplied lyophilized and is reconstituted by addition of water. After reconstitution, FabULOUS is stable for at least 1 month at +4-8°C. The product is shipped cold and should be stored at -20°C upon arrival.

Unit Definition

One unit digests ≥ 95% of 1 µg human IgG1 when incubated in PBS with 5 mM DTT or TCEP, pH 7.4 at 37°C for 1 hour.

Buffers and Reducing agents

FabULOUS digests IgG in commonly used buffers with pH ranging from 6.5 to 8.0 and best activity is obtained at 37°C. The enzyme requires reducing agent in the digestion reaction and depending on the reducing conditions, there is a chance that the interchain thiols will be reduced.

How to Order

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Please do not hesitate to contact us if you need a quotation or have inquiries on price of bulk quantities.



Product Specifications


Certificate of Analysis

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

FabULOUS enzyme reaction is inhibited with iodoacetamide, iodo acetic acid or lowering pH below 3.


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