Q. What are the major theoretical models that try to explain the formation of the enzyme-substrate complex?

There are two major models that explain the formation of the enzyme-substrate complex: the key and lock model and the induced fit model. In the key and lock model the enzyme has a region with specific spatial conformation for the binding of the substrate. In the induced fit model the binding of the substrate induces a alteration in the spatial configuration of the enzyme for the substrate to fit.