Is the formation of the ES complex essential for catalysis?

The chemical or metabolic conversion refers to a reaction. The chemical which is converted into a product is called a ‘substrate’. Hence enzymes, i.e. proteins with three dimensional structures including an ‘active site’, convert a substrate (S) into a product (P). S. The substrate ‘S’ has to bind the enzyme at its ‘active site’ within a given cleft or pocket. The substrate has to diffuse towards the ‘active site’. There is thus, an obligatory formation of an ‘ES’ complex. E stands for enzyme.