Given the task definition and input, reply with output. In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: Allopurinol, as an inhibitor of xanthine oxidase:
Options: <1> It is suicidal, reversible. <2> It is suicidal, irreversible. <3> It is analogous to the transition state, reversible. <4> Inhibits the enzyme by proteolysis. <5> Allopurinol does not inhibit that enzyme.
2