Which test demonstrates whether a specific enzyme or drug is having its intended effect?

The correct answer is the activity assays, as these tests are specifically designed to measure the functional effect of an enzyme or drug on a specific substrate or within a biological system. By assessing changes in activity, such as reaction rates or product formation, activity assays can provide direct evidence of whether the enzyme or drug is working as intended. This allows researchers and clinicians to evaluate the efficacy of the treatment or enzyme in real-time, leading to informed decisions about its use and potential adjustments as needed.

In contrast, potency assays primarily focus on determining the minimal amount of a drug or enzyme required to elicit a specific response, which does not directly measure if the desired effect is achieved. ELISA (Enzyme-Linked Immunosorbent Assay) is utilized mainly for quantifying proteins, such as antibodies or antigens, rather than evaluating enzymatic or drug activity. Gel electrophoresis is a technique used for the separation and analysis of nucleic acids or proteins based on size and charge, but it does not assess functional effects or activity directly. Therefore, activity assays stand out as the most suitable method for demonstrating whether a specific enzyme or drug is having its intended effect.