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CEDIA, cloned enzyme donor immunoassay

المؤلف:  Sue Jickells , Adam Negrusz (Editors)

المصدر:  Clarkes Analytical Forensic Toxicology

الجزء والصفحة:  38

2026-11-05

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CEDIA, cloned enzyme donor immunoassay

A more recent variant on the homogeneous enzyme immunoassay is the CEDIA system. This system, like EMIT, uses the binding of an antibody to influence the activity of an enzyme. Competition for binding by drug present in the sample results in an increase in enzyme activity. The CEDIA principle (Henderson et al. 1986) relies on the spontaneous complementation of two genetically engineered fragments of β-galactosidase from Escherichia coli. The polypep tide chain of the enzyme is presented as two inactive fragments, the large fragment, termed enzyme acceptor (EA), and a small fragment, enzyme donor (ED), which contains the 5% of enzyme missing from the EA portion. By conjugating hapten to the ED fragment, the addition of antibodies that bind the hapten can prevent the formation of an intact, and therefore active, enzyme. Any drug present in the sample competes for antibody-binding sites, such that an increase in drug concentrations yields less binding of antibody to the ED fragment and therefore results in more enzyme activity which can be monitored spectrophotometrically.