Enzymes are proteins with high specificity, ie each catalyzes only one type of chemical reaction, or a small number of reactions. This is due to its shape, which presents on the surface molecular fittings, the active sites or centers where the substrates or reagents attach. An example of this is the ability of an enzyme to select a specific substrate from the myriad of molecules floating around its environment.
Therefore, substrates other than those that fit into the active sites of a specific enzyme cannot be part of that reaction, there must be another enzyme to catalyze its reaction. The specificity of enzymes for their substrates is similar to the specificity between a lock and its key.
Operons afford the organism the opportunity to
simultaneously regulate transcription of multiple genes, whose products are
active in the same process. Operons lead to the synthesis of groups of functionally
related enzymes, usually from a single mRNA transcript hence makes regulation of
the genes highly efficient.
