FabULOUS® Enzyme

FabULOUS enzyme 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 reduced condition for activity and reaction is performed in the presence of 1-5 mM DTT or TCEP at neutral pH.



FabULOUS is supplied as lyophilized powder with no preservatives added and is available in a 2000 units pack size.

FabULOUS contains a His-tag and can easily be removed after digestion.

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Detailed Information

FabULOUS (SpeB) is an enzyme for digestion of IgG in the upper hinge region. All subclasses of human (except hIgG4), 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.. and on mouse IgG1 ..KPCIC / TVPEVS..

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 (Table 1). Optimal activity is obtained at 37°C. FabULOUS requires reducing agent in the digestion reaction (Table 2). The reducing agent present during the reaction is likely to reduce interchain thiols.

The molecular weight of FabULOUS is 28 724 Da and the enzyme contains a His-tag.


The enzyme is reconstituted by addition of water and after reconstitution FabULOUS is stable for 1 month at +4-8°C. The product is shipped on ice and should be stored at -20°C upon arrival.

Unit definition

One unit digests ≥ 95% of 1µg human or mouse IgG when incubated in 10 mM Tris, 150 mM NaCl pH 7.4 at 37°C for 1 hour.

Buffers and Reducing agents

FabULOUS cleaves 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.



Product specifications


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FAQ and Support


We have not found that FabULOUS (SpeB) digest human IgG4. For other subclasses and species tested please visit

Find all FAQ here

Patent and Disclaimer


The trademark FabULOUS is the property of Genovis AB.

For research use only. Not intended for any animal or human therapeutic diagnostic use.