Structure of The lac Operon
- The lac operon consists of three structural genes, and a promoter, a terminator, regulator, and an operator. The three structural genes are: lacZ, lacY, and lacA.
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- lacZ encodes β-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and galactose.
- lacY encodes β-galactoside permease (LacY), a membrane-bound transport protein that pumps lactose into the cell.
- lacA encodes β-galactoside transacetylase (LacA), an enzyme that transfers an acetyl group from acetyl-CoA to β-galactosides.
Only lacZ and lacY appear to be necessary for lactose catabolism.
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