What effect do drug-resistance mutations have on enzyme activity?

Drug-resistance mutations often occur in enzymes that are targets for specific inhibitors, such as those used in cancer therapy or antibiotic treatment. When these mutations arise, they can lead to structural changes in the enzyme that effectively alter its binding interactions.

The correct answer indicates that these mutations can prevent competitive inhibitors from binding to the enzyme. Competitive inhibitors typically bind to the active site, competing with the substrate for access. When a drug-resistance mutation occurs, the binding affinity of the inhibitor may be decreased, allowing the enzyme to maintain its activity even in the presence of that drug. However, it's also possible for these mutations to confer a reduction in overall enzyme activity due to changes in the enzyme's conformation or function, which can affect how well the enzyme catalyzes its reaction.

This dual effect—where the mutation prevents inhibitor binding while potentially impacting overall activity—is an important concept in understanding drug resistance in biochemical pathways, particularly in pathogens or tumor cells that evolve to survive treatment.