Enzyme

An enzyme is a biological catalyst, typically a protein (though some RNA molecules can also act as enzymes), that accelerates chemical reactions in living organisms without being consumed or permanently altered in the process. Enzymes are essential for virtually all metabolic processes, enabling reactions to occur at rates sufficient to sustain life. They are involved in critical physiological processes such as respiration, digestion, DNA replication, detoxification, muscle contraction, and nerve function. Each cell contains thousands of different enzymes; each enzyme is specific to a particular reaction or type of reaction due to its unique structure and active site.

Varies greatly depending on the specific enzyme and drug interaction. Common mechanisms include competitive inhibition, non-competitive inhibition, allosteric modulation, and irreversible inhibition.