Substances that plug up an enzyme's active site are enzyme ________.inhibitorsproductssubstratescatalysts

The substances that plug up an enzyme's active site are enzyme inhibitors.

Explanation:

Enzyme inhibitors are molecules that bind to enzymes and reduce their activity. They can occupy the active site of the enzyme, preventing the substrate from binding. This obstruction can significantly decrease the rate of the reaction that the enzyme catalyzes. There are different types of enzyme inhibitors, such as competitive inhibitors, which compete with the substrate for the active site, and non-competitive inhibitors, which bind to a different site on the enzyme.

In summary, enzyme inhibitors are crucial in regulating metabolic pathways and can be found in various biological and pharmaceutical applications.