Mitochondrial carbonic anhydrase that catalyzes the reversible conversion of carbon dioxide to bicarbonate/HCO3 (PubMed:7937950). Mitochondria are impermeable to HCO3, and thus this intramitochondrial carbonic anhydrase is pivotal in providing HCO3 for multiple mitochondrial enzymes that catalyze the formation of essential metabolites of intermediary metabolism in the urea and Krebs cycles (By similarity). H(+) + hydrogencarbonate = CO2 + H2O High in liver, also detected in heart, lung, kidney, spleen and intestine. Belongs to the alpha-carbonic anhydrase family.