Competitive Inhibitor

Competitive inhibitors are molecules that resemble the shape of an enzyme's true substrate closely enough that they can compete with it to occupy the enzyme's active site. Because the inhibitor and substrate are competing for the same limited number of active sites, this type of inhibition can be overcome (out-competed) by sufficiently raising the concentration of the true substrate. A well-known example given in the text is RuBisCO (ribulose bisphosphate carboxylase-oxygenase), the enzyme that catalyses the reaction between carbon dioxide and its acceptor molecule during photosynthesis: RuBisCO is competitively inhibited by oxygen competing with carbon dioxide for the same active site inside the chloroplast (this competition is the biochemical basis of photorespiration). Another classic example is malonate, which competit …