Carbonic anhydrases reaction medium

The enzyme has been found in corals (Goreau, 1959), annelids (Clark, 1975), crustaceans (Costlow, 1959), molluscs (Wilbur, 1972, for references), and echinoderms (Heatfield, 1970). In all cases, sulfanilamide inhibitors of the enzyme added to the medium reduced the rate of calcification at least 50%, indicating that catalysis by carbonic anhydrase is required for the normal rate of mineralization. In theory, the reactions should occur without enzyme catalysis and this appears to be true. Various mechanisms of action have been suggested (e.g., Goreau, 1959 Istin and Girard, 1970b) but the exact role of carbonic anhydrase remains uncertain. 

Carbon dioxide transport by the blood.—If pure water is exposed to carbon dioxide at a partial pressure of 40 mm. Hg, which is the usual alveolar value, the gas dissolves until the resulting solution of carbonic acid has a pH of 4-7 for ordinary temperature. If, however, blood be exposed to the same partial pressure of gas the resulting solution has a pH of about 7 4, which is only slightly less than the value for untreated blood. That is to say, blood has a considerable buffering power for H-ions. But blood is the transport medium for the elimination of carbon dioxide by the lungs, and must be provided with some mechanism for the rapid escape of the gas. When blood is exposed to reduced pressure carbon dioxide is released in two ways (i) rapidly from the carbonic acid, and (ii) slowly from the acid carbonates in solution. The speed of the first reaction led Meldrum and Roughton to suspect the existence of a catalyst, which they later isolated from the red corpuscles, and named carbonic anhydrase because it catalysed the reversible reaction,... 

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