This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Biochemistry
Which of the following is known as suicidal enzyme? 
Select and explain. 
A. Lipoxygenase, B. Cyclooxygenase, C. Thromboxane synthatase, D. 5' nucleotidase
B: Cyclooxygenase
Answer: B: Cyclooxygenase 
Explanation: Suicidal enzyme is one, which undergoes self-destruction in order to terminate its own acitivity, e.g. Cyclooxygenase. Suicidal Inhibition is conversion of a substrate by the enzyme into a metabolite, which is a potent inhibitor of the enzyme; example: Xanthine oxidase conves allopurinol to alloxanthine (oxypurinol), which is a more potent inhibitor of allopurinol. Cycloorygenase is known as suicide enzyme because it catalyzes its own destruction. REF: Lippincott book of biochemistry 6th ed.