Abstract
Carbonic anhydrases (CA) are enzymes which catalyze the interconversion of CO2 and bicarbonate ions. CAs are found in all independently living organisms in which they regulate pH homeostasis and assist in fundamental metabolic pathways. The same reaction mechanism has been reinvented at least four times in the course of evolution, leading to three distinct major classes of alpha, beta and gamma CAs, totally unrelated in structural and sequence levels, and minor classes delta (Co/Zn enzyme, in marine phytoplankton), and zeta (Cd/Zn enzyme in marine diatoms). All CAs are metalloproteins, with bound zinc in most cases.In insects, CAs of the α and β classes have been identified together with the enzymatically inactive carbonic anhydrase-related proteins (CARPs). To elucidate the relationship of these genes, a phylogenetic analysis of these sequences was carried out. We found various lineage-specific gene duplications and losses. In addition, we discovered high divergence in the number and location of exons in one family of orthologs (CAH-1). A strong functional conservation of the CARP sequences is also demonstrated.
