Enzymes that have achieved kinetic perfection are those whose catalytic velocity is determined solely by the rate at which the substrate is encountered in solution. In other words, their catalytic velocity is diffusion-limited. Such an enzyme would have a kcat/KM value that was equal to k1, which is the rate of formation of the ES (enzyme-substrate) complex.
For such a kinetically perfect enzyme, every encounter between the substrate and enzyme must be productive. In order to accomplish this, attractive electrostatic forces may be utilized in order to ensure that the substrate “bumps into” the active site of the enzyme. These electrostatic forces are termed “Circe effects,” a title that was introduced by the enyzmologist William P. Jencks. These electrostatic forces are named after the Greek goddess, Circe, who attracted Odyssseus’s men to her house and changed them into pigs.