The main explanation of the hypothesis of enzyme activity control in prokaryotes is the operon hypothesis.
According to this theory, genes are of two types:
1. Structural genes that contain information about the location of amino acids in the protein molecule of the enzyme.
2. Regulator genes that perform regulatory functions.
Structural genes are located nearby and form a block - operon. At the beginning of the structure of the operon is a gene - an operator that turns structural genes on and off. The operator controls the regulator gene. The regulator gene encodes the synthesis of a repressor protein. The repressor in an active form blocks transcription: the reading of genetic information stops and the entire operon is turned off. As long as the repressor is linked to the operator gene, the operon is off. Upon transition to an inactive form, the gene operator is released, the operon is turned on, and the appropriate RNA is synthesized, followed by the enzyme synthesis process.