A  

Non-competitive inhibitors bind at an allosteric site, lowering the maximal velocity (Vmax) because some enzyme molecules are rendered inactive, but they do not alter substrate affinity, so Km remains unchanged. Studies show acetazolamide acts non-competitively, reducing Vmax without affecting Km for target enzymes, including carbonic-anhydrase–related systems [Norby, 1981, PMID 7235014; Pullan, 1984, PMID 6431986].