Explain the mechanism of enzyme catalysis.

(N/A) There are a number of cavities present on the surface of colloidal particles of enzyme. These cavities are of characteristic shape and possess active groups such as $-NH_2$,$-COOH$,$-SH$,$-OH$,etc. These are actually the active centres on the surface of enzyme particles. The molecules of the reactant which have complementary shape,fit into these cavities like a key fits into a lock. On account of the presence of active groups,an activated complex is formed which then decomposes to yield the products.
Thus,the enzyme catalysed reactions may be considered to proceed in two steps.
Step-$1$: Binding of enzyme to substrate to form an activated complex.
$E + S \rightleftharpoons ES^{*}$
Step-$2$: Decomposition of the activated complex to form product.
$ES^{*} \rightarrow E + P$