Drugs are chemical agent’s which produces a measurable reaction in a
biological system. Drugs are targeted to protein structures in order to produce
a pharmacological effect. Enzymes are proteins which act as biological
catalysts which alter the rate of biological reaction and are unchanged at the
end of the reaction, this allows reaction to occur at sufficient speed. Enzymes
can be the target of drugs in order to catalyse reactions which lead to
formation of metabolites which can be the biologically active form and bring
about a pharmacological effect and also aid the breakdown and elimination of
the drug.(https://www.drugbank.ca/documentation). This is the case in the P450 cytochrome enzyme’s
which is present in the liver; drugs encounter these enzymes when undergoing
first pass Metabolism. A drug can also have an inhibitory effect on enzyme this
is the case in the anti-cancer drug Tyrosine Kinases Inhibitor which inhibits
the enzyme tyrosine kinases preventing the phosphorylation of tyrosine residue substrates
effecting cell proliferation. This effect may be exhibited when drug binds to
enzyme linked receptor, this alters the shape, leading to signal to be
transduced and enzymatic activation or inhibition to occur. An enzyme may be
targeted by an enzyme linked receptor or a GPCR which acts as a relay to
activate enzymes to produce a second messenger which lead to the intended
response. (https://moodle.kent.ac.uk/external/mod/book/view.php?id=2396&chapterid=79)
