Reversible hydration of carbon dioxide. This isoform ensures the supply of bicarbonate for pep carboxylase. H(+) + hydrogencarbonate = CO2 + H2O Photosynthesis; C4 acid pathway. Additional isoforms seem to exist. According to EST sequences. Strongly expressed in aerial tissues including leaves, stems, flowers and siliques. Accumulates in mesophyll cells. Expression reduced by 20% under dark conditions. Belongs to the beta-class carbonic anhydrase family. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus. Truncated N-terminus.