CA2 (carbonic anhydrase 2) is a cytosolic enzyme that catalyzes the reversible hydration of carbon dioxide to bicarbonate and protons, playing essential roles in pH regulation and ion transport 1. The enzyme functions through zinc-dependent catalysis and can also hydrate cyanamide to urea 2. CA2 stimulates chloride-bicarbonate exchange activity of SLC26A6 and contributes to intracellular pH regulation in duodenal epithelium during proton-coupled peptide absorption 3. The enzyme is essential for bone resorption and osteoclast differentiation, and is involved in regulating fluid secretion into the anterior chamber of the eye 4. CA2 deficiency is associated with osteopetrosis, autosomal recessive 3, a rare bone disease characterized by impaired bone resorption due to osteoclast dysfunction. The enzyme's wide tissue distribution and multiple cellular locations (cytoplasm, plasma membrane, apical cell regions) reflect its fundamental role in cellular pH homeostasis and bicarbonate transport processes. CA2's involvement in bone metabolism makes it clinically significant for understanding bone remodeling disorders and potential therapeutic targets.