inducible enzyme

In biochemistry, an inducible enzyme is one whose synthesis is increased when cells are exposed to a specific substance, known as an inducer. This substance is typically the substrate upon which the enzyme acts. For example, E. coli bacteria produce the enzyme (\beta)-galactosidase only when lactose (its substrate) is present in their environment.123

This mechanism is a form of metabolic control that prevents the cell from wasting energy by producing enzymes it doesn't currently need. The process is regulated by genes that produce repressor proteins. When an inducer is present, it binds to the repressor, preventing it from blocking the DNA region responsible for enzyme synthesis. This allows the enzyme to be produced. This contrasts with repression, where a repressor protein directly inhibits enzyme synthesis.14