Carbonic anhydrase 4(CA4) is an enzyme that belongs to the alpha-carbonic anhydrase family. CA4 consists of a signal peptide (residues1-17), an ectodomain (residues18-277) and a propeptide (residues278-305), which is removed in the mature form. it is predominantly expressed in the embryo. CA4 can catalyzes the reversible reaction of CO2+H2O=HCO3-+H+, and stimulates the sodium/bicarbonate transporter activity of SLC4A4. Studies have shown that this protein have a role in inherited renal abnormalities of bicarbonate transport. Alpha-carbonic anhydrase family participate in avariety of biological processes, including respiration, calcification, acid-base balance, bone resorption, and the formation of aqueous humor. They show extensive diversity in tissue is attribution and in their sub cellular localization.