Aim: 

Carbonic anhydrases (CAs) are enzymes that catalyze the reversible hydration of CO2 playing a role in pH homeostasis, respiratory gas exchange and ion transport. For their ubiquitous distribution and their multifunctional role, these proteins are well suited for eco-physiological and molecular evolution studies, since CAs may play a pivotal role for the adaptation. Our research is focused on the characterization of aminoacid and nucleotide sequences of the CA in two Antarctic fish species: Trematomus eulepidotus and T. lepidorhinus, adapted to low water temperature (–1.9°C).

Methods: 

Total mRNA was purified from gills of specimens sampled in the Ross Sea (Terra Nova Bay) and the cDNA was sequenced by a combination of RT-PCR and RACE techniques. The obtained sequences were compared with those available in GenBank.

Results: 

Multiple alignment comparison and phylogenetic analyses reveal that CA sequences from T. eulepidotus e T. lepidorhinus are very closely related to those of other teleosts, with particular reference to amino acids involved in catalytic properties. Distinct aminoacid sequence features, shared with other antarctic teleosts but different from non-antarctic species, can be singled out by sequence comparisons.

Conclusion: 

The physiological significance of such aminoacid substitutions, possibly related to cold adaptation, is investigated. To this aim, three-dimensional protein structure homology analyses are in progress (PNRA and MIUR grants).