From Proteopediaproteopedia link
Human Carbonic Anhydrase II in complex with novel inhibitors
[CAH2_HUMAN] Defects in CA2 are the cause of osteopetrosis autosomal recessive type 3 (OPTB3) [MIM:259730]; also known as osteopetrosis with renal tubular acidosis, carbonic anhydrase II deficiency syndrome, Guibaud-Vainsel syndrome or marble brain disease. Osteopetrosis is a rare genetic disease characterized by abnormally dense bone, due to defective resorption of immature bone. The disorder occurs in two forms: a severe autosomal recessive form occurring in utero, infancy, or childhood, and a benign autosomal dominant form occurring in adolescence or adulthood. Autosomal recessive osteopetrosis is usually associated with normal or elevated amount of non-functional osteoclasts. OPTB3 is associated with renal tubular acidosis, cerebral calcification (marble brain disease) and in some cases with mental retardation.    
[CAH2_HUMAN] Essential for bone resorption and osteoclast differentiation (By similarity). Reversible hydration of carbon dioxide. Can hydrate cyanamide to urea. Involved in the regulation of fluid secretion into the anterior chamber of the eye. 
Publication Abstract from PubMed
Human carbonic anhydrases (CAs) are well studied targets for the development of inhibitors for pharmaceutical applications. The crystal structure of human CA II has been determined in complex with two CA inhibitors (CAIs) containing conventional sulfonamide and thiadiazole moieties separated by a -CF2- or -CHNH2- spacer group. The structures presented here reveal that these spacer groups allow novel binding modes for the thiadiazole moiety compared with conventional CAIs.
X-ray crystallographic studies reveal that the incorporation of spacer groups in carbonic anhydrase inhibitors causes alternate binding modes.,Fisher SZ, Govindasamy L, Boyle N, Agbandje-McKenna M, Silverman DN, Blackburn GM, McKenna R Acta Crystallogr Sect F Struct Biol Cryst Commun. 2006 Jul 1;62(Pt, 7):618-22. Epub 2006 Jun 10. PMID:16820676
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.