The crystal structure of the human carbonic anhydrase II in complex with 4-amino-6-chloro-benzene-1,3-disulfonamide
[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
Three benzene-1,3-disulfonamide derivatives were investigated for their interaction with 12 mammalian alpha-carbonic anhydrases (CAs, EC 18.104.22.168), and three bacterial/archaeal CAs belonging to the alpha-, beta-, and gamma-CA class, respectively. X-ray crystal structure of the three inhibitors in complex with the dominant human isozyme CA II revealed a particular binding mode within the cavity. The sulfonamide group in meta-position to the Zn(2+)-coordinated SO(2)NH(2) moiety was oriented toward the hydrophilic side of the active site cleft, establishing hydrogen bonds with His64, Asn67, Gln92, and Thr200. The plane of the phenyl moiety of the inhibitors was rotated by 45 degrees and tilted by 10 degrees with respect to its most recurrent orientation in other CA II-sulfonamide complexes.
Carbonic anhydrase inhibitors: inhibition of human, bacterial, and archaeal isozymes with benzene-1,3-disulfonamides--solution and crystallographic studies.,Alterio V, De Simone G, Monti SM, Scozzafava A, Supuran CT Bioorg Med Chem Lett. 2007 Aug 1;17(15):4201-7. Epub 2007 May 18. PMID:17540563
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.