This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Enzymes, Subject name: Biochemistry
Which of the following is a suicidal enzyme? 
Select and explain. 
A. Lipoxygenase, B. Cyclooxygenase, C. 5 ' nucleotidase, D. Thromboxane synthase
B: Cyclooxygenase
Answer: B: Cyclooxygenase 
Explanation: The suicidal enzyme is one, which undergoes self-destruction in order to terminate its own activity, e.g. cyclooxygenase Switching off of prostaglandin activity is paly achieved by a remarkable propey of cyclooxygenase, that of self-catalyzed destruction, i.e. it's a suicidal enzyme. Suicidal inhibition is the conversion of a substrate by the enzyme into a metabolite, which is a potent inhibitor of the enzyme. e.g., xanthine oxidase conves allopurinol to alloxanthine (oxypurinol), which is a more potent inhibitor of allopurinol.