From Proteopediaproteopedia link
N-Hydroxyurea, a versatile zinc binding function in the design of metalloenzyme 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
N-Hydroxyurea binds both to carbonic anhydrase (CA) and to matrix metalloproteinases (MMPs). X-ray crystallography showed N-hydroxyurea to bind in a bidentate mode by means of the oxygen and nitrogen atoms of the NHOH moiety to the Zn(II) ion of CA, participating in a network of hydrogen bonds with a water molecule and Thr199. A derivatized N-hydroxyurea showed low-micromolar affinity for several CAs. This simple zinc binding function may be exploited for obtaining potent metalloenzyme inhibitors, due to its versatility of binding to the metal ion present in the active site of such enzymes.
N-hydroxyurea--a versatile zinc binding function in the design of metalloenzyme inhibitors.,Temperini C, Innocenti A, Scozzafava A, Supuran CT Bioorg Med Chem Lett. 2006 Aug 15;16(16):4316-20. Epub 2006 Jun 12. PMID:16759856
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.