Abstract
Carbonic anhydrases (CAs) are a family of metalloenzymes that can catalyze the reversible interconversion of CO2/HCO3–, ubiquitously present in both prokaryotes and eukaryotes. In the present study, a CA II (designated as HdhCA II) was sequenced and characterized from the mantle tissue of the Pacific abalone. The complete sequence of HdhCA II was 1,169 bp, encoding a polypeptide of 349 amino acids with a NH2-terminal signal peptide and a CA architectural domain. The predicted protein shared 98.57% and 68.59% sequence identities with CA II of Haliotis gigantea and Haliotis tuberculata, respectively. Two putative N-linked glycosylation motifs and two cysteine residues could potentially form intramolecular disulfide bond present in HdhCA II. The phylogenetic analysis indicated that HdhCA II was placed in a gastropod clade and robustly clustered with CA II of H. gigantea and H. tuberculata. The highest level of HdhCA II mRNA expression was detected in the shell forming mantle tissue. During ontogenesis, the mRNA of HdhCA II was detected in all stages, with larval shell formation stage showing the highest expression level. The in situ hybridization results detected the HdhCA II mRNA expression in the epithelial cells of the dorsal mantle pallial, an area known to express genes involved in the formation of a nacreous layer in the shell. This is the first report of HdhCA II in the Pacific abalone, and the results of this study indicate that this gene might play a role in the shell formation of abalone.
Highlights
Carbonic anhydrases (CAs) are zinc ion-containing metalloenzymes that can catalyze the essential hydration of CO2 through the simple chemical reaction: CO2 + H2O HCO3− + H+ (Lindskog and Silverman, 2000)
The results of the analysis revealed that HdhCA II mRNA was expressed throughout the early developmental stages in a ubiquitous fashion (Figure 6)
Based on the in situ results of the present study, we speculated that HdhCA II might be involved in the shell formation by catalyzing the hydration of CO2. This is the first study of molecular characterization and expression of HdhCA II mRNA in different tissues and developmental stages of the Pacific abalone
Summary
Carbonic anhydrases (CAs) are zinc ion-containing metalloenzymes that can catalyze the essential hydration of CO2 through the simple chemical reaction: CO2 + H2O HCO3− + H+ (Lindskog and Silverman, 2000). CAs play an essential role in multiple physiological processes such as pH regulation, electrolyte balance, ionic transportation, carboxylation or decarboxylation reactions, Carbonic Anhydrase II in Pacific Abalone biocalcification, and tumorigenicity (Supuran, 2008, 2011; Alterio et al, 2009). CAs are important components of the CO2-concentrating mechanisms in different groups of algae. CA seems to be contributed to shell formation via catalyzing the hydration of CO2 (Nielsen and Frieden, 1972). This enzyme has been shown to be an effective catalyst in the calcification mechanism of coral (Rahman and Oomori, 2010)
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