Feedback inhibition

Feedback inhibition is a biological process that occurs when the end-product of a metabolic pathway inhibits an earlier step in the pathway, preventing the pathway from producing more end-product than needed. This is a type of negative feedback and is important in maintaining homeostasis in a cell.

Overview

In feedback inhibition, the final product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway. This type of inhibition is an example of allosteric regulation, where the shape of the enzyme is altered to decrease its activity.

Mechanism

The mechanism of feedback inhibition involves the binding of the end-product to an allosteric site on an enzyme earlier in the pathway. This changes the shape of the enzyme, making it less able to bind to its substrate, and thus slowing down or stopping the pathway. This prevents the overproduction of the end-product and ensures that resources are not wasted.

Role in Homeostasis

Feedback inhibition plays a crucial role in maintaining homeostasis within a cell. By preventing the overproduction of certain substances, it helps to maintain a balance within the cell. This is particularly important in the regulation of metabolism, where the overproduction of certain metabolites can be harmful to the cell.

Examples

One example of feedback inhibition is the regulation of the amino acid phenylalanine. The enzyme phenylalanine hydroxylase, which converts phenylalanine to tyrosine, is inhibited by high levels of tyrosine. This prevents the overproduction of tyrosine and the depletion of phenylalanine.

Another example is the regulation of the tricarboxylic acid cycle (TCA cycle), also known as the Krebs cycle. High levels of ATP, the end-product of the TCA cycle, inhibit the enzyme citrate synthase, preventing the overproduction of ATP.

See also

• Allosteric regulation
• Enzyme inhibition
• Homeostasis
• Metabolic pathway
• Negative feedback

Feedback inhibition Resources
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