Enzyme acceptor

Anti-cAMP modification Bead/plate None Cryptate Streptavidin Enzyme acceptor Plate... 

The ProLabel peptide can be chemically conjugated or recombinantly fused to various biomolecules. To probe molecular interactions, EEC assays are based on a competition between the free and the ProLabel peptide-conjugated form of the biomolecule involved in the interaction under study. Bound to its interaction partner, the ProLabel-labelled biomolecule is not able to complement with the Enzyme Acceptor. Therefore the signal generated by the P-galactosidase is proportional to the concentration of the free biomolecule in the assay."... 

This technique uses two different inactive enzyme fragments, a large fragment called enzyme acceptor (EA) and a very small fragment called enzyme donor (ED). Those fragments can associate to give an active enzyme. 

Figure 9-15 CEDIA and EMIT homogeneous immunoassays. A, Enzyme acceptor ED, enzyme donor.

The cloned enzyme donor immunoassay (CEDIA) technique for T4 measurement is based on the use of inactive fragments of p-galactosidase called enzyme acceptor (EA) and enzyme donor (ED). In this method, T4 in a serum sample competes with ED-labeled T4 for a hmited number of anti-T., binding sites. As the concentration of unlabeled T4 increases, less ED-labeled T4 binds to the antibody and more reassociates with EA to form an active enzyme. The catalytic activity of the holoenzyme increases in proportion to the amount of T4 in the sample. This method has been adapted for use on on routine chemistry analyzers. ... 

The [3-galactosidase analog consists of two subunits a large dimeric polypeptide (200 kDa), denoted enzyme acceptor (EA)2, and a small polypeptide (20 kDa), denoted enzyme donor (ED). (EA)2 and ED are enzymatically inactive but spontaneously associate to give enzymatically active tetramers. In CEDIA assays, [45,46] the hapten or analyte is covalently linked to the ED, and an analyte-specific antibody is used to inhibit the assembly of the enzymatically active tetramers. Analyte in a patient s serum competes with the analyte in the analyte-ED conjugate for antibody, modulating the amount of active B-... 

Several hematologists are of the view that the primary step in hemostasis is the adhesion of platelets to exposed collagen fibers. " It has been proposed that the adhesion is due to the formation of an enzyme-acceptor complex between the incomplete carbohydrate chains (galactosyl residues) of collagen and an enzyme of the platelet membrane (glycosyl transferase). Platelets in contact with collagen fibers contract and release adenosine diphosphate (ADP) as well as other platelet constituents. ADP causes more platelets to adhere and the autocatalytic reaction proceeds towards the formation of a hemostatic plug. 

Our two approaches lead to the same conclusion. The persistence of terminal label on chased chains shows that these must grow at the enzyme-proximal end. Likewise the absence of dADP-ribose residues on completed chains implies that chains cannot accrete residues at the enzyme-dist (i.e. 2 OH) end. Enzyme proximal chain growth implies that the enzyme must act in some sense like a ribosome, alternating Ae growing chain between two attachment sites. Clearly these can be on the same enzyme molecule. The enzyme constmcts poly(ADP-ribose) by itself, without a partner, and in particular without any other non-enzyme "acceptor". 

Tetrahydrofolic acid is also an enzymic acceptor of a formimino group from formiminoglycine or from formiminoglutamic acid. The product, 5-formimino-5,6,7,8-tetrahydrofolic acid, is converted in acidic solution to anhydrofolinic acid and ammonium ion and has a half-Ufe of about i h at 37° over a pH range i of 5-9. Aerobic oxidation of tetrahydrofolic acid produces />-aminobenzoy lutamic acid and a number of pteridines, including xanthopterin . ... 

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