Irreversible inhibition of carbonic anhydrase by the carbon dioxide analog cyanogen.

Cyanogen (C2N2), a molecule with properties remarkably similar to carbon dioxide, differentially inhibits three of the four carbonic anhydrases reported here. Bovine carbonic anhydrase II shows 97% loss of esterase activity with no concommitant loss in hydratase activity. The hydratase and esterase activities of human carbonic anhydrase I are decreased by 80% and 55% respectively. Canine carbonic anhydrase shows similar results to human carbonic anhydrase I, retaining 29% hydratase and 62% esterase activity. Rabbit carbonic anhydrase sustained no loss of either hydratase or esterase activity. This inhibition occurs by an irreversible modification of the enzymes. The kinetic parameters for modified and unmodified enzymes were altered in a way that reflects the characteristic effect for each carbonic anhydrase.