The term for a protein that binds to and inhibits the activity of enzymes is called an inhibitor. Inhibitors can be classified into two main types: competitive inhibitors, which compete with the substrate for the active site of the enzyme, and non-competitive inhibitors, which bind to a different site, altering the enzyme's function. Understanding enzyme inhibitors is crucial in biochemistry and pharmacology since they can be used therapeutically to regulate metabolic pathways or control disease processes.