Urease
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The active site of ureases is located in the α (alpha) subunits. It is a bis-μ-hydroxo dimeric nickel center, with an interatomic distance of ~3.5 Å.cite-ref-karplus-5-5[5] > The Ni(II) pair are weakly antiferromagnetically coupled.cite-ref-14[14] X-ray absorption spectroscopy (XAS) studies of Canavalia ensiformis (jack bean), Klebsiella aerogenes and Sporosarcina pasteurii (formerly known as Bacillus pasteurii)cite-ref-benini-s-1999-15-0[15] confirm 5–6 coordinate nickel ions with exclusively O/N ligation, including two imidazole ligands per nickel.cite-ref-pmid20046957-9-1[9] Urea substrate is proposed to displace aquo ligands.
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