What term describes a substance that slows or blocks enzyme action?

A substance that slows or blocks enzyme action is known as an enzyme inhibitor. Enzyme inhibitors can bind to enzymes and reduce their activity by either altering the enzyme's active site, where substrates bind, or by preventing the substrate from binding altogether. This interference can result in a decrease in the rate of the chemical reaction that the enzyme catalyzes.

Enzyme inhibitors can work in different ways, such as competitive inhibition, where the inhibitor competes with the substrate for the active site, or non-competitive inhibition, where the inhibitor binds to a site other than the active site, altering the enzyme's shape and function. This regulatory mechanism is crucial in biological systems, allowing for the modulation of metabolic pathways and the maintenance of homeostasis.

The other terms refer to different concepts within enzyme activity. Activators and enzyme stimulators enhance enzyme action, promoting substrate binding and increasing the reaction rate. Coenzymes, on the other hand, are organic molecules that assist enzymes in catalyzing reactions, often serving as carriers for chemical groups or electrons.