What can activate an enzyme that has a low catalytic rate?

An allosteric modulator can activate an enzyme with a low catalytic rate by binding to a site other than the active site, known as the allosteric site. This binding causes a conformational change in the enzyme, which can enhance its activity. Allosteric activation often increases the enzyme's affinity for its substrate or increases the rate of the reaction, thus effectively boosting the catalytic rate. This mechanism allows for fine-tuning of enzyme activity in response to changes in the cellular environment or metabolic needs.

In contrast, a competitive inhibitor works by binding to the active site, obstructing substrate binding, which can actually decrease enzyme activity rather than activate it. A substrate analog mimics the substrate but does not necessarily activate the enzyme; it may compete with the substrate and slow down catalysis depending on the context. A negative feedback regulator typically works to inhibit an enzyme's activity once a sufficient amount of product has been formed, ensuring that the pathway is properly regulated and does not overproduce the end product.