Conventional ureases possess dinuclear nickel active sites that are oxygen-stable and require a set of accessory proteins for metallocenter biosynthesis. By contrast, oxygen-labile ureases have active sites containing dual ferrous ions and lack a requirement for maturation proteins. The structures of the two types of urease are remarkably similar, with an active site architecture that includes two imidazoles and a carboxylate ligand coordinated to one metal, two imidazoles coordinated to the second metal, and a metal-bridging carbamylated lysine ligand. The electronic spectrum of the diferric form of the enzyme resembles that of methemerythrin. Resonance Raman spectroscopic analyses confirm the presence of a µ-oxo ligand and indicate the presence of one or more terminal solvent ligands.

传统的脲酶具有氧稳定的双核镍活性位点，并且需要一组用于金属中心生物合成的辅助蛋白。相比之下，氧不稳定脲酶具有含有双亚铁离子的活性位点，并且不需要成熟蛋白。两种类型的脲酶的结构非常相似，活性位点结构包括两个咪唑和一个与一种金属配位的羧酸盐配体、两个与第二种金属配位的咪唑，以及一个金属桥氨甲酰化赖氨酸配体。该酶的二价铁形式的电子光谱类似于甲基菊酯的电子光谱。共振拉曼光谱分析证实了 µ-oxo 配体的存在，并表明存在一种或多种末端溶剂配体。