Enzyme-linked cleavage

Accurate measurement of proinsulin has been difhcult for several reasons the blood concentrations are low antibody production is difficult most antisera cross-react with insulin and C-peptide, which are present in much higher concentrations the assays measure intermediate cleavage forms of proinsulin and reference preparations of pure proinsulin are not readily available. However, a more sensitive nonequiUb-rium RIA method for measuring proinsiilin was developed by adsorbing the initial antiserum with biosynthetic human C-peptide coupled to agarose to eliminate cross-reactivity with C-peptide.An enzyme-linked immunosorbent assay (ELISA) has been described that employs an antibody to C-peptide as the coating antibody and antiinsulin antibody for detection. The detection limit is 0.25 pmol/L. ... 

DNA cleavage by E. coli topoisomerase I usually requires denaturant treatment (Depew et al., 1978), but with short oligonucleotides as substrates, cleavage can be achieved under native conditions (Tse-Dinh et al., 1983). Under these conditions, it has also been possible to show transfer of the enzyme-linked oligonucleotide to an acceptor DNA bearing a 3 -hydroxyl group (Y.-C. Tse-Dinh, personal communication). 

Methods have been developed to detect ASOs in plasma and other biological samples, based on hybridization with labeled complementary probes [89], The probes are tagged at one end with biotin and the other end with digoxigenin. After hybridization and binding to neutravidin-coated 96-well plates, nuclease SI is added to degrade unhybridized probe. Anti-digoxigenin antibodies and enzyme-linked secondary antibodies are then added sequentially, followed by enzyme substrate (for example, AttoPhos, which fluoresces after enzymatic cleavage) for detection and quantitation [60, 61]. 

Detection of Internucleosomal Cleavage by Enzyme-Linked Immunosorbent Assay (ELISA). Induction of apop-... 

Enzyme Cross-linking Cleavage Poly-acrylamide Gel dissolution [11]... 

Enzyme (MMPs) Cross-linking Cleavage PEG Gel dissolution (irreversible) [12]... 

Enzyme Cross-linking Cleavage of Peptide Hydrogel [14,... 

FIGURE 23.15 The reactions of glycogen debranching enzyme. Transfer of a group of three o -(l 4)-linked glucose residues from a limit branch to another branch is followed by cleavage of the o -(l 6) bond of the residue... 

Figure 42-12. Structure of human proinsulin. Insulin and C-peptide molecules are connected at two sites by dipeptide links. An initial cleavage by a trypsin-like enzyme (open arrows) followed by several cleavages by a car-boxypeptidase-like enzyme (solid arrows) results in the production of the heterodimeric (AB) insulin molecule (light blue) and the C-peptide.

Complement is not a single protein but comprises a group of functionally linked proteins that interact with each other to provide mar of the effector functions of humoral immunity and inflammation. Most of the components of the system are present in the serum as proenzymes, i.e. enzyme precursors. Activation of a complement molecule occurs as a result of proteolytic cleavage of the molecule, which in itself confers proteolytic activity on the molecule. Thus, many components of the system serve as the substrate of a prior component and, in turn, activate a subsequent component. This pattern of sequential activation results in the system being called the complement cascade. ... 

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