Carbonic Anhydrase-Related Protein 11 (CA11) is a secreted protein member of the α-carbonic anhydrase family. Carbonic Anhydrases (CAs) are a large family of zinc metalloenzymes that catalyze the reversible hydration of carbon dioxide. They participate in a variety of biological processes, including respiration, calcification, acid-base balance, bone resorption, and the formation of aqueous humor, cerebrospinal fluid, saliva, and gastric acid. CA11 is expressed abundantly in the brain with moderate expression also present in spinal cord and thyroid. CA11 may play a general role in the central nervous system.