This system is found in E.Coli and several other enteric bacteria.
It is essential for the transportation and metabolism of lactose in those bacteria.
A set of genes are involved in this process.
Lac operon consists of three coding zones - lac Z, lac Y, and lac A.
Degradation of lactose is carried out by the lac Z gene which codes for Beta-galactosidase.
Transportation of lactose is a function of the lac Y gene that codes for lactose permease.
Lac A encodes for galactoside acetyltransferase.
There is also a lac I gene which acts as lac repression and functions in the absence of lactose, it inhibits the expression of genes that codes for proteins involved in the lactase metabolism in bacteria.
Role of lactose in lac operon:
The substrate required for the beta-galactosidase enzyme to function is lactose.
It also functions as an inducer for lac operon.
It allows the transcription to start by inactivating the repressor and thus allowing the RNA polymerase to act on the promotor site.
