Carbonic anhydrase catalyzes the reversible reaction of CO2? H2O = HCO3-? H , which is fundamental to many processes such as respiration, renal tubular acidification and bone resorption. Carbonic Anhydrase?VII encoded by the CA7 gene is a cytosolic protein predominantly expressed in the salivary gland. CA7 may have additional tissue distributions and functions. For example, studies with CA inhibitors provide evidence that human CA7 is the CA isozyme responsible for the anticonvulsant/antiepileptic activity of sulfonamides and sulfamates. In fact, CA7 has been shown in a rat model to act as a developmental switch in GABAergic signaling in neurons. The activity of recombinant mouse CA7 was measured by its ability to hydrolyze 4-Nitrophenyl acetate (4-NPA) to 4-Nitrophenol. The reaction was performed in 12.5 mM Tris, 75 mM NaCl, pH 7.5 (assay buffer), initiated by addition 50 μL of various concentrations of CA7 (diluted by assay buffer) to 50 μL of 2 mM substrate 4-NPA (100 mM stock in Acetone, diluted by assay buffer). Incubated at 37℃ for 5min, then read at a wavelength of 400 nm.