Beta-galactosidase Enzyme Acceptor


Catalog #: P2010005 (1 mg)

Beta-galactosidase Enzyme Acceptor (also known as Omega Domain) is the larger fragment of the Beta-galactosidase enzyme. This fragment can associate with the smaller fragment of the Beta-galactosidase enzyme (Alpha peptide, enzyme donor) and reconstitute an active Beta-galactosidase enzyme.

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Beta-galactosidase Enzyme Acceptor (Omega peptide)

Catalog # P2010005
Size 1.0 mg
Other Names Beta-galactosidase Omega Domain
Supplied as White lyophilized powder.
Molecular Weight 113 kDa (997 amino residues)
Purity >95% (SDS PAGE)
Storage -20°C. Avoid repeated freeze/thaw cycles.
Suggested buffer Beta-galactosidase Enzyme Acceptor Stabilization Buffer (B2010002)
Keywords Beta-galactosidase Omega Domain, Enzyme Acceptor, alpha complementation, LacZ.
Related products Beta-galactosidase Enzyme Donor (Alpha Peptide), Beta-galactosidase Enzyme Acceptor Stabilization Buffer, Beta-galactosidase Alpha Complementation Kit.


Download Alpha Complementation Product Line Brochure.

About Beta-galactosidase Alpha Complementation

Beta-galactosidase Alpha-Complementation is a biochemical phenomenon first documented by Agnes Ullmann, while working in the lab of François Jacob and Jacques Monod. By means of molecular cloning, the native E. coli β-galactosidase enzyme can be split in two inactive fragments of different sizes. The smaller fragment, known as the alpha-peptide or enzyme donor, is about 100 amino residues in length and is inactive on its own (incapable of hydrolyzing a β-galactosidase substrate). The larger fragment, known as the omega fragment or enzyme acceptor, is about 900 amino residues in length and is also inactive on its own. Upon mixing the enzyme donor with the enzyme acceptor, the β-galactosidase enzyme is reconstituted and is now capable of hydrolyzing colorimetric substrates such as ONPG.

Both enzyme donor and enzyme acceptor can be cloned and expressed in special E. coli strains to yield highly pure, zero-background enzyme fragments (i.e. an enzyme donor and enzyme acceptor without measurable catalytic activities, when assayed individually). Interestingly, it was discovered that various analytes can be conjugated to the enzyme donor moiety and the enzyme donor-enzyme acceptor association modulated by an analyte-binding molecule (such as an antibody). As a result, an alpha-complementation-based assay can be developed.


  • Kras, E. (2019). Beta-galactosidase: properties, structure and functions. New York: Nova Science Publishers.
  • Arndt, T. (2017). Cloned Enzyme Donor Immunoassay. Lexikon Der Medizinischen Laboratoriumsdiagnostik, 1–2.
  • Jeon, S. I., Yang, X., and Andrade, J. D. (2004). Modeling of homogeneous cloned enzyme donor immunoassay. Analytical Biochemistry, 333(1), 136–147.
  • Tachi, T., Kaji, N., Tokeshi, M., and Baba, Y. (2009). Microchip-based Homogeneous Immunoassay Using a Cloned Enzyme Donor. Analytical Sciences, 25(2), 149–151.
  • Khanna, P. L., and Worthy, T. E. (1993). CEDIA: A Recombinant-Based Homogeneous Enzyme Immunoassay.

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