<prompt> Which of the following is known as suicidal enzyme? AIIMS November 2013, May 2013LipoxygenaseCyclooxygenaseThromboxane synthatase5 nucleotidase  <response>: Ans. b. Cyclooxygenase Ref: Harper 27e p204 Harrison 18e p146Cyclooxygenase is a suicidal enzyme.Suicidal enzyme is one. which undergoes self-destruction in order to terminate its own acitivity. e.g. Cyclooxygenase.Switching off of prostaglandin activity is partly achieved by a remarkable property of cyclooxygenaseQ, that of self-catalyzed destruction, i.e. it is a suicidal enzyme.Suicidal inhibition is conversion of a substrate by the enzyme into a metabolite, which is a potent inhibitor of the enzyme; example: Xanthine oxidase converts allopurinol to alloxanthine oxypurinol, which is a more potent inhibitor of allopurinol. 