Effects of selected water toxicants on the in vitro activity of fish carbonic anhydrase.

Carbonic anhydrase (CA, carbonate hydro-lyase EC 4.2.1.1) from lysed red blood cells of the channel catfish (Ictalurus punctatus) was studied to determine physico-chemical kinetic properties and relative sensitivity to 56 chemicals of significance in water quality research. In general, enzyme activity was strongly reduced by heavy metal inorganic cations; less strongly by organometallic cations, some anions, and certain pesticides; and weakly inhibited by light metal cations and organometallic and organic compounds. Dose--response curves were qualitatively similar in most cases.