The evolution of metazoan aα-carbonic anhydrases and their roles in calcium carbonate biomineralization

The carbonic anhydrase (ca; ec 4.2.1.1) superfamily is a class of ubiquitous metallo-enzymes that catalyse the reversible hydration of carbon dioxide. the aα-ca family,present in all metazoan clades,is a key enzyme involved in a wide range of physiological functions including ph regulation,respiration,photosynthesis,and biocalcification. this paper reviews the evolution of the aα-ca family,with an emphasis on metazoan aα-ca members involved in biocalcification. phylogenetic analyses reveal a complex evolutionary history of aα-cas,and suggest aα-ca was independently co-opted into a variety of skeleton forming roles (e.g. as a provider of hco3- ions,a structural protein,a nucleation activator,etc.) in multiple metazoan lineages. this evolutionary history is most likely the result of multiple gene duplications coupled with the insertion of repetitive or non-repetitive low-complexity domains (rlcds/lcds). these domains,of largely unknown function,appear to be lineage-specific,and provide further support for the hypothesis of independent recruitment of aα-cas to diverse metazoan biocalcification processes. an analysis of aα-ca sequences associated with biocalcification processes indicates that the domains involved in the activity and conformation of the active site are extremely conserved among metazoans. © 2014 le roy et al.; licensee biomed central ltd.