The conversion of C02 and H20 into carbonic acid during the formation of aqueous humor is catalysed by which one of the following enzymes

Ans. is 'c' ie carbonic anhydrase (Ref: Parson, 19/e, p166; Kanski, 5/e, p193; Chatterjee Shinde Biochemistry. 6/e, p629).Nowhere could 1 find a direct answer. The points in favour of the above answer are --Of all the above options, carbonic anhydrase is the only enzyme which catalyzes the reversible reaction :CO2+H2O =H2 CO3Kanski writes - "Aqueous humor is actively secreted by the non pigmented epithelium as a result of a metabolic process that depends on several enzyme systems, specially the Na+/K+ ATPase pump, which secretes Na+ ions into the posterior chamber. Water follows passively along the osmotic gradient. Carbonic anhydrase also plays a role, but the precise mechanism is uncertain."Parson writes - "Carbonic anhydrase inhibitors block the action of carbonic anhydrase and reduce the production of aqueous in the eye."