Overview of Antigen Detection Through Enzymatic Activity

The use of enzymes along with immunoglobulins to identify specific substances emerged with the work by Nakane and Pierce, who labeled an immunoglobulin with the peroxidase enzyme rather than with a fluorescent compound (1 ). The difficulty with this approach lies in attaching a relatively large molecule, like an enzyme, to another large molecule, like an immunoglobulin, with neither molecule losing the ability to function. In this case, labeling can occur without appreciable functional loss. The labeled antibody is still able to bind the antigen, and the attached enzyme is still able to catalyze the oxidative reaction. This direct labeled technique was the forerunner of numerous other methods that bring enzymes and antibodies together to allow the enzyme action to identify the location of the antigen through the antibody intermediary.