Although internally-duplicated, alpha-type carbonic anhydrase (CA) from Dunaliella species (Dsp-CA) can be expressed in Escherichia coli system, the produced amount is not sufficient for practical application. Here, we demonstrated to express the N- and C-half CA domains of Dsp-CA as distinct proteins to increase the expression levels further. The purified N-half CA domain (Dsp-CA-n) showed very low detectable activities of esterase or CO2 hydratase. In contrast, the purified C-half CA domain (Dsp-CA-c) retained both activities, which were enhanced by the presence of Dsp-CA-n. The expression levels of both domains were increased by 2-5-fold as compared to that of Dsp-CA. The CA activity was successfully reconstituted by mixing the two domains, N- and C-half domains, and more activity level was achieved than dimeric intact CA. These results newly suggest that the produced amount and activity of a duplicated CA are enhanced successfully by expressing each half CA domain individually and in vitro reconstitution. (C) 2012 Elsevier Ltd. All rights reserved.