Committed step

In biochemistry, the committed step (also known as the first committed step) is an effectively irreversible, enzyme-catalyzed reaction that occurs at a branch point during the biosynthesis of some molecules.

Often, the first committed step is regulated by processes such as feedback inhibition and activation.

Such regulation ensures that pathway intermediates do not accumulate, a situation that can be wasteful or even harmful to the cell.

The term has also been applied to other processes that involve a series of steps.

For example, the binding of egg and sperm can be thought of as the first committed step in metazoan fertilization.

Schematic representation of a metabolic branch point . The numbers represent chemical compounds, whereas the letters represent enzymes that catalyze the conversion indicated by the nearby arrow. In this scheme, enzyme c catalyzes the committed step in the biosynthesis of compound 6.