CARBONIC ANHYDRASE CATALYZED HYDROLYSIS OF 2-HYDROXY-5-NITRO-ALPHA-TOLUENESULFONIC ACID SULTONE

An ionizable group in bovine carbonic anhydrase (BCA) with a pK of 7.3 appears to be involved in the enzyme-catalyzed hydrolysis of 2-hydroxy-5-nitro-α-toluenesulfonic acid sultone (I). Similar observations have been reported previously for the pH-rate behavior of the BCA-catalyzed hydration of CO2, hydration of carbonyl compounds, and hydrolysis of nitrophenyl esters of carboxylic acids. The BCA-catalyzed hydrolysis of I is subject to sulfonamide inhibition as are the other reactions mentioned above. Also, human carbonic anhydrases B and C have been demonstrated to be effective catalysts for the hydrolysis of I. On the basis of our observations taken in conjunction with those of other investigations we have proposed that a zinc bound hydroxide ion is the active catalytic species in carbonic anhydrase action and we have suggested a cyclic mechanism for the carbonic anhydrase catalyzed solvolysis of I, involving no net proton transfer to the solvent. © 1969, American Chemical Society. All rights reserved.