Allosteric inhibition

Allosteric inhibition is a process that directly impacts the biochemical activity within a cell. It is a form of enzyme regulation that occurs when a regulatory molecule binds to an enzyme in a spot different from the active site (the allosteric site). This binding changes the conformation of the enzyme, or its three-dimensional shape, which can increase or decrease its activity. In the case of allosteric inhibition, the activity of the enzyme is decreased.

Mechanism of Allosteric Inhibition

The mechanism of allosteric inhibition involves the binding of an allosteric inhibitor to the allosteric site of an enzyme. This binding induces a conformational change in the enzyme structure, which in turn affects the active site of the enzyme. The altered active site can no longer bind to the substrate, or if it does bind, it does so less efficiently, resulting in decreased enzyme activity.

Role in Metabolic Pathways

Allosteric inhibition plays a crucial role in the regulation of metabolic pathways. It helps maintain homeostasis within the cell by controlling the production of certain substances. For example, if a pathway produces too much of a certain product, that product may act as an allosteric inhibitor, binding to an enzyme at the beginning of the pathway. This inhibits the enzyme's activity and slows down the pathway, reducing the amount of product made.

Examples of Allosteric Inhibition

One example of allosteric inhibition is the regulation of the enzyme phosphofructokinase, which plays a key role in the process of glycolysis. When levels of ATP (adenosine triphosphate) are high, ATP molecules bind to an allosteric site on phosphofructokinase. This changes the shape of the enzyme and inhibits its activity, slowing down the rate of glycolysis and conserving the cell's energy resources.

Allosteric Inhibition vs. Competitive Inhibition

Allosteric inhibition should not be confused with competitive inhibition, another form of enzyme regulation. In competitive inhibition, a molecule similar to the substrate binds to the active site of the enzyme, preventing the substrate from binding and thus inhibiting the enzyme's activity. Unlike allosteric inhibition, competitive inhibition does not involve a change in the enzyme's conformation.