Substrate analogs can act as competitive inhibitors of an enzymatic reaction.
[3] The maximum rate (Vmax) remains the same[4] while the intended substrate’s affinity (measured by the Michaelis constant KM) is decreased.
[5] This means that less of the intended substrate will bind to the enzyme, resulting in less product being formed.
In addition, the substrate analog may also be missing chemical components that allow the enzyme to go through with its reaction.
[9] An example of a substrate analog that is also a gratuitous inducer is IPTG (isopropyl β-D-1-thiogalactopyranoside), a substrate analog and gratuitous inducer of β-galactosidase activity.