Drugs are chemical agent’s which produces a measurable reaction in abiological system. Drugs are targeted to protein structures in order to producea pharmacological effect. Enzymes are proteins which act as biologicalcatalysts which alter the rate of biological reaction and are unchanged at theend of the reaction, this allows reaction to occur at sufficient speed. Enzymescan be the target of drugs in order to catalyse reactions which lead toformation of metabolites which can be the biologically active form and bringabout a pharmacological effect and also aid the breakdown and elimination ofthe drug.
(https://www.drugbank.ca/documentation). This is the case in the P450 cytochrome enzyme’swhich is present in the liver; drugs encounter these enzymes when undergoingfirst pass Metabolism.
A drug can also have an inhibitory effect on enzyme thisis the case in the anti-cancer drug Tyrosine Kinases Inhibitor which inhibitsthe enzyme tyrosine kinases preventing the phosphorylation of tyrosine residue substrateseffecting cell proliferation. This effect may be exhibited when drug binds toenzyme linked receptor, this alters the shape, leading to signal to betransduced and enzymatic activation or inhibition to occur. An enzyme may betargeted by an enzyme linked receptor or a GPCR which acts as a relay toactivate enzymes to produce a second messenger which lead to the intendedresponse.