Purification and characterization of an extracellular carbonic anhydrase from Pseudomonas fragi

Extracellular carbonic anhydrase was purified from Pseudomonas fragi isolated from CaCO₃ enriched soil samples. The enzyme is induced in presence of CaCO₃ and is envisaged to play an important role in bicarbonate ion transport. The 75% ammonium sulphate dialysate was purified by single step affinity chromatography with 86% yield. It is a trimeric protein having a subunit molecular weight of 31.0 kDa and was stable at pH 7.0–8.5 and temperature 35–45 °C. Lead, mercury and EDTA had an inhibitory effect on CA activity, whereas zinc, iron and cadmium increased it. The presence of esterase activity along with IC₅₀ of sulphonamides and anionic inhibitors indicated that CA from P. fragi belonged to α-class. The CA stability in presence of different salts, as well as in alkaline pH and high temperature makes it a potential candidate to be exploited for biomimetic CO₂ sequestration.