Potential application of carbonic anhydrase activity in bioassay and biomarker studies

Carbonic anhydrase (CA) (EC 4.2.1.1), a ubiquitous enzyme in bacteria, plant, and animal kingdoms, catalyses the reversible hydration of CO2 to produce H+ and using zinc as cofactor. CA plays a fundamental role in a number of physiological processes, such as respiration, ionic transport, acid–base regulation, and calcification. The aim of the present work was to investigate the sensitivity of this enzyme to heavy metals with a view to possible future applications of CA activity inhibition measurement in biomonitoring as either an in vitro bioassay or a biomarker. CA activity was determined by modifying a previously described electrometric method: briefly, CA activity units were calculated from the rate of H+ production in the reaction mixture (where CO2 was present as a substrate) against a blank containing the specific CA inhibitor acetazolamide. As regards the possible application as an in vitro bioassay, the sensitivity to heavy metals (cadmium, mercury, and copper) of the commercially available purifi...