Carbonic anhydrase (CA) is a zinc-containing metalloenzyme that catalyzes the interconversion of CO₂ and HCO₃^-.  CA is a ubiquitous enzyme found in different cell types of almost all organisms, including bacteria, green algae, animals, and plants.  The widespread abundance of CA in different organisms and the occurrence of multiple isoforms suggests that this enzyme has many physiological functions such as pH homeostasis, photosynthesis, calcification, inorganic carbon assimilation and the metabolism of urea, glucose and lipids.  CA plays a critical role in biological systems because the uncatalyzed interconversion between CO₂ and HCO₃^- is slow when compared to the required rate in living cells.

In photosynthetic organisms, CA's role in concentrating inorganic carbon for efficient fixation has been studied most.  Recently, additional roles for CA in non photosynthetic tissues of plants have been proposed (i.e., root nodules).  We isolated cDNAs encoding functional CA enzymes from cotyledons of dark grown cotton seedlings, and are exploring roles for CA in seed development, germination, and post-germinative seedling growth.  A combination of physiological, biochemical and molecular approaches are employed to understand more about this enzyme's multiple functions in plant cells.