How do mutations in enzymes contribute to drug resistance?

Mutations in enzymes can play a significant role in the development of drug resistance, and a crucial mechanism for this is the alteration of the enzyme's active site. When mutations occur, they may change the shape or chemical properties of the active site, the region of the enzyme where substrates or drugs bind. If the active site is altered, it can prevent drugs from effectively interacting with the enzyme, making it impossible for them to bind and exert their intended effect.

This resistance allows the organism, whether bacteria, viruses, or cancer cells, to survive in the presence of a drug that would normally inhibit or kill it, leading to treatment failures. Such mutations are often selected for in environments where the drug is present, as those organisms that develop mutations granting them resistance have a survival advantage.

In contrast, concepts such as generalizing enzyme functions or enhancing drug binding don't accurately reflect the typical impact of mutations related to resistance. Generally, mutations that reduce substrate specificity or increase binding do not contribute to resistance; they might actually make the organism more susceptible to the drug rather than promote resistance.