PANEN33 RTP SLOT When lactose is present in the cell the enzyme β-galactosidase is produced to convert lactose into glucose or galactose. When lactose is absent in the cell the lac repressor inhibits the production of the enzyme β-galactosidase to prevent any inefficient processes within the cell. The lac operon is used in the biotechnology industry for production of recombinant proteins for therapeutic use.|Their Lives are Far from Normal