Task: Question Answering
Input (English): Question: In general, allosteric enzymes: 
 Options:  <1> They join the effectors in the active center. <2> They form covalent bonds with their negative effectors. <3> They originate hyperbolic curves of speed versus substrate concentration. <4> They change their conformation when they join the effectors. <5> They are irreversibly modified when they are inhibited.
Output (English): 4