Cloning, Expression Analysis and Enzyme Activity Assays of the α-Carbonic Anhydrase Gene from Chlamydomonas sp. ICE-L.

The α-carbonic anhydrase (α-CA) is a zinc ion-containing enzyme that catalyzes the hydration of carbon dioxide. In this paper, a full-length α-CA gene was cloned from Chlamydomonas sp. ICE-L using RT-PCR and RACE-PCR for bioinformatic analysis. The α-CA open reading frame obtained by PCR was cloned into a vector and transformed into Escherichia coli to generate α-CA-producing bacteria. The α-CA was highly expressed upon induction with isopropyl-β-d-thiogalactoside (IPTG) at a final concentration of 0.8 mM. A single band with a molecular weight of approximate 40 kDa expressed in the recombinant E. coli strain harboring the α-CA vector was observed in SDS-PAGE analysis. The carbon dioxide hydration activity and esterase activity of α-CA expressed by the recombinant strain were 0.404 U/mg and 0.319 U, respectively. In addition, three conditions, temperature, salinity and UVB radiation exposure, were selected to analyze α-CA transcription levels by qRT-PCR. The results suggested UVB exposure increased the expression of relative mRNA; meanwhile, the α-CA mRNA expression was rapidly induced by temperature and salinity stress, indicating that Chlamydomonas sp. ICE-L might modulate the α-CA mRNA expression to adapt to the extreme environments.