In case of enzymatic reaction the enzyme is so built that it binds to the substrate in a specific manner. An enzyme carries out specific leach only .Enzymatic reaction involves following steps (Lock and Key Model)-
Step (i) : Binding of substrate(S) to enzyme (E) to form complex
E + S → [ES] (Enzyme substrate complex)
Step (ii) : Product formation in complex
[ES] → EP (Enzyme product complex)
Step (iii) : Dissociation of enzyme product complex, leaving enzyme unchanged
EP → E + P
The specificity of enzyme is due to presence of some specific regions called active site on their surface.