Regulatory enzyme
![Chymotrypsinogen (the precursor of Chymotrypsin). Painted in red the residue ILE16 and in green the residue ARG15 both involved in the enzyme activation. In dark blue the residue ASP 194 that will later interact with ILE 16.](/Images/godic/202502/06/Chymotrypsinogen5951.jpg")
5951.jpg")
![Gamma-Chymotrypsin, a complex of Alpha-Chymotrypsin. Images modified from pdb](/Images/godic/202502/06/Chymotrypsin_activated5952.jpg")
A regulatory enzyme is an enzyme in a biochemical pathway which, through its responses to the presence of certain other biomolecules, regulates the pathway activity. This is usually done for pathways whose products may be needed in different amounts at different times, such as hormone production. Regulatory enzymes exist at high concentrations (low Vmax) so their activity can be increased or decreased with changes in substrate concentrations.