Beta-galactosidase Enzyme Donor – Catalog #: P2010004 (250 μg)

Beta-galactosidase Enzyme Donor (alpha peptide) provides the donor fragment required for α-complementation of E. coli β-galactosidase. The supplier lists a defined 250 μg fill (Catalog P2010004), supplied as a white lyophilized powder with a reported molecular weight of 11 kDa comprising 99 amino acids. A unique central cysteine is engineered into the sequence to facilitate analyte conjugation strategies, and storage is specified at −20 °C with avoidance of repeated freeze–thaw. A Beta-galactosidase Enzyme-Donor Stabilization Buffer (B2010001) is identified as the suggested buffer for handling and storage.

In research workflows, this donor fragment reconstitutes enzymatic activity upon association with the complementary omega (acceptor) fragment, enabling qualitative readouts tied to β-gal substrate turnover. Because the donor and acceptor are individually inactive, background from residual catalytic activity can be minimized prior to complementation, which is helpful during method development and training exercises. Practical setup typically begins with small pilot titrations to determine the donor:acceptor ratio suited to the sample matrix and detection chemistry, while documenting pH, ionic strength, incubation times, and temperature history. The lyophilized format supports precise aliquoting and flexible buffer selection; reconstitution in the suggested stabilization buffer can help standardize handling during optimization.

Typical applications include assembling alpha-complementation assay prototypes, constructing qualitative controls for platform checks, and exploring conjugation workflows that leverage the engineered cysteine for coupling to analytes or carrier molecules. When integrating into SOPs, labs often track lot identifiers and record time-at-temperature to ensure reproducibility across runs and operators. Within research-only boundaries, the clear specification set (size, format, molecular characteristics, storage, and suggested buffer) makes this donor fragment a dependable, documentation-friendly component for laboratories standardizing β-galactosidase alpha-complementation methods.

Why researchers choose this product:

• Defined 250 μg fill of the alpha (donor) fragment for α-complementation workflows
• Supplied as white lyophilized powder for precise aliquoting and flexible buffer selection
• 11 kDa, 99-aa entry with engineered central cysteine supports conjugation strategies
• Specified storage at −20 °C; avoid repeated freeze–thaw as listed
• Listed Enzyme-Donor Stabilization Buffer (B2010001) aids consistent handling

This product is for Research Use Only (RUO). It is not intended for diagnostic or therapeutic use.

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.

References

• 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.

Brochure

• Download Alpha Complementation Product Line Brochure