Metal toxicity causes oxidative stress in fish. This situation is a potential risk factor for humans and other living feeding on contaminated fish. In this study, the inhibition effects of heavy metals on carbonic anhy- drase enzyme from the corb fish gill were investigated. The carbonic anhydrase enzyme was purified from gill of corb fish with a specific activity of 2093,9 EUmg−1 and 86,51% yield and approximately 160 fold using Sep- harose 4B–L-tyrosine sulfanilamide affinity chromatography method. SDS–polyacrylamide gel electrophoresis showed a single band corresponding to a molecular weight of approximately 30,8 kDa. Inhibitory effects of metals (Ag+, Cu2+, Pb2+, Zn2+, Cd2+, Ni2+) on CA activity were determined at different concentrations using the hydratase method under in vitro conditions. Consequently, in vitro inhibition rank order was determined as Ag+> Cu2+> Pb2+> Zn2+ > Cd2+> Ni2+. From these results, we showed that Ag+ is the most potent inhibitor of CA enzyme.