Extracellular carbonic anhydrase was purified from Pseudomonas fragi isolated from CaCO(3) enriched soil samples. The enzyme is induced in presence of CaCO(3) 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 degrees 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 IC(50) of sulphonamides and anionic inhibitors indicated that CA from P. fragi belonged to a-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 CO(2) sequestration. (C) 2009 Elsevier Ltd. All rights reserved.