A cloned enzyme donor immunoassay (CEDIA) is a competitive homogenous enzyme immunoassay. This assay makes use of two component fragments of an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...

which are each individually inactive. Under the right conditions in solution these fragments can spontaneously reassemble to form the active enzyme. For use in biochemical assays one of the enzyme fragments is attached to an analyte of interest. The analyte-enzyme-fragment-conjugate is still able to reassemble with the other enzyme fragment to form an active enzyme. However it is unable to do this if the analyte is bound to an antibody. To determine the quantity of analyte in a sample, an

aliquot Aliquot ( la, a few, some, not many) may refer to: Mathematics *Aliquot part, a proper divisor of an integer *Aliquot sum, the sum of the aliquot parts of an integer *Aliquot sequence, a sequence of integers in which each number is the aliquot sum ...

of sample must be added to a solution containing enzyme-fragment-analyte-conjugate, the other enzyme fragment, antibody directed against the analyte and substrate for the enzyme reaction. Competition for the antibody occurs between the analyte in the sample and the enzyme-fragment-analyte-conjugate. High concentrations of analyte in the sample lead to a relatively small amount of the enzyme-fragment-analyte-conjugate being prevented from forming active enzyme and therefore high enzyme activity. Conversely, low concentrations of analyte in the sample lead to a relatively large amount of the enzyme-fragment-analyte-conjugate being prevented from forming active enzymes and therefore low enzyme activity.

References

{{Reflist Immunologic tests