Final answer:
The commonly used enzyme in enzyme immunoassays, as used in ELISAs, is horseradish peroxidase, which facilitates the detection of target molecules by catalyzing the production of a measurable signal from a chromogenic substrate.
Step-by-step explanation:
In an enzyme immunoassay, commonly used in enzyme-linked immunosorbent assays (ELISAs), the detection antibody is typically conjugated with an enzyme that acts as a signal generator. This enzyme catalyzes a reaction to convert a substrate into a measurable end product, often a colored or fluorescent one. The common enzymes used in this assay format include horseradish peroxidase and alkaline phosphatase. Specifically, horseradish peroxidase is widely utilized due to its ability to catalyze a reaction that produces a measurable and high-contrast signal. This enables the detection of target molecules with high sensitivity and specificity.
The enzyme that is commonly used in such assays and is specifically mentioned in the question is horseradish peroxidase (c). This enzyme, when used with the suitable chromogenic substrate, generates a colored product, the intensity of which can be measured colorimetrically to determine the presence and quantity of the antigen of interest.