What is an example of allosteric regulation in metabolic pathways?

Allosteric regulation refers to the modulation of protein activity through the binding of effector molecules at sites other than the active site, leading to a conformational change that affects the protein's function. In the context of metabolic pathways, phosphofructokinase-1 (PFK-1) plays a critical role in glycolysis and is subject to allosteric regulation.

The inhibition of PFK-1 by ATP serves as an important regulatory mechanism. When ATP levels are high, the energy needs of the cell are being met, and further glycolysis is not necessary. ATP binds to an allosteric site on PFK-1, reducing its activity and thus slowing down the glycolytic pathway. This effectively prevents the unnecessary expenditure of resources when energy is in surplus.

The other examples mentioned do involve important regulatory mechanisms, but they do not represent classic allosteric regulation in the same way. For instance, while ADP does act as an activator of PFK-1, signaling low energy levels in the cell, it does so through an increase in overall enzymatic activity rather than inhibition. Additionally, glucose-6-phosphate's inhibition of hexokinase is a classic example of feedback inhibition rather than allosteric regulation per