Development and pharmacological characterization of a modified procedure for the measurement of carbonic anhydrase activity.

Carbonic anhydrases (CAs) are a family of zinc metalloenzymes of molecular mass 30-60 kDa; seven different isoenzymes belong to this family (Okuyama et al., 1992, Proc Natl Acad Sci USA 89:1315-1319). They may be broadly recognized according to the efficiency with which they catalyze the reversible interconversion of CO2 and HCO3-, and they differ in physicochemical properties, in sensitivity to various inhibitors and in their subcellular localization; cytoplasmic (CA I, CA II, CA III, and CA VII), cell-surface membrane (CA IV), and mitochondrial (CA V) and secretory (CA VI) isoenzymes have been described. Several methods are reported in the literature for the measure of CA enzymatic activity; they may be broadly divided into two categories: those based on the measure of pH variation (pH-stat and colorimetric assays) (Wu et al., 1993, J Ocular Pharm 9:97-108; Maren, 1991, Molec Pharmacol 41:419-426) and the ones in which CO2 production is measured through pCO2 sensors (Botrè and Botrè, 1990, Anal Biochem 185:254-264).