lac operon

The lac operon is an operon required for the transport and metabolism of lactose in Escherichia coliand some other enteric bacteria. It consists of three adjacent structural genes, lacZ, lacY and lacA. The genes encode β-galactosidase, lactose permease, and thiogalactoside transacetylase.

In its natural environment, the lac operon allows for the effective digestion of lactose. The lactose permease, which sits in the cytoplasmic membrane, transports lactose into the cell. β-galactosidase, a cytoplasmic enzyme, subsequently cleaves lactose into glucose galactose. However it would be wasteful to produce the enzymes when there is no lactose available or if there is a more preferable energy source available such asglucose. Gene regulation of the lac operon was the first genetic regulatory mechanism to be elucidated and is one of the foremost examples of prokaryotic gene regulation.