Lac Operon @biogeny net
The lac operon (lactose operon) is an operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria. It has three adjacent structural genes, lacZ, lacY, and lacA. The genes encode β-galactosidase, lactose permease, and galactoside O-acetyltransferase, respectively. In its natural environment, the lac operon allows for the effective digestion of lactose. Lactose permease, which is embedded in the cytoplasmic membrane, transports lactose into the cell. β-galactosidase, a cytoplasmic enzyme, subsequently cleaves lactose into glucose and 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 as glucose. Gene regulation of the lac operon was the first genetic regulatory mechanism to be understood clearly, so it has become a foremost example of prokaryotic gene regulation. It is often discussed in introductory molecular and cellular biology classes at universities for this reason.