CA2(carbonic anhydrase II ) is also named as Car2, CA-II, CAII and belongs to the alpha-carbonic anhydrase family. It reversibly hydrates CO2 in cellular ion transport and homeostasis. CA2 is essential for bone resorption and osteoclast differentiation. It regulates SLC9A1 activity via a phosphorylation-regulated CAII binding site in SLC9A1 tail. It also may be involved in the development of brain.