Dihydropyrimidinase, a dimetalloenzyme containing a carboxylated lysine within the active site, is a member of the cyclic amidohydrolase family, which also includes allantoinase, dihydroorotase, hydantoinase, and imidase. Unlike all known dihydropyrimidinases, which are tetrameric, pseudomonal dihydropyrimidinase forms a dimer at neutral pH. In this paper, we report the crystal structure of P. aeruginosa dihydropyrimidinase at pH 5.9 (PDB entry 5YKD). The crystals of P. aeruginosa dihydropyrimidinase belonged to space group C222₁ with cell dimensions of a = 108.9, b = 155.7, and c = 235.6 Å. The structure of P. aeruginosa dihydropyrimidinase was solved at 2.17 Å resolution. An asymmetric unit of the crystal contained four crystallographically independent P. aeruginosa dihydropyrimidinase monomers. Gel filtration chromatographic analysis of purified P. aeruginosa dihydropyrimidinase revealed a mixture of dimers and tetramers at pH 5.9. Thus, P. aeruginosa dihydropyrimidinase can form a stable tetramer both in the crystalline state and in the solution. Based on sequence analysis and structural comparison of the dimer-dimer interface between P. aeruginosa dihydropyrimidinase and Thermus sp. dihydropyrimidinase, different oligomerization mechanisms are proposed.

中文翻译：

---

铜绿假单胞菌PAO1中双氢嘧啶酶的pH依赖性低聚反应的结构基础。

二氢嘧啶酶是一种在活性位点内包含羧化赖氨酸的双金属酶，是环状酰胺水解酶家族的成员，其还包括尿囊素酶，二氢乳清酶，乙内酰脲酶和酰亚胺酶。不同于所有已知的四聚体二氢嘧啶酶，假单烷二氢嘧啶酶在中性pH下形成二聚体。在本文中，我们报告了铜绿假单胞菌二氢嘧啶酶在pH 5.9（PDB条目5YKD）的晶体结构。铜绿假单胞菌二氢嘧啶酶的晶体属于空间群C 222 ₁，细胞尺寸为a  = 108.9，b  = 155.7和c  = 235.6。铜绿假单胞菌的结构二氢嘧啶酶的分辨率为2.17Å。晶体的不对称单元包含四个晶体学上独立的铜绿假单胞菌二氢嘧啶酶单体。纯化的铜绿假单胞菌二氢嘧啶酶的凝胶过滤色谱分析显示，在pH 5.9下，二聚体和四聚体的混合物。因此，铜绿假单胞菌二氢嘧啶酶可以在结晶状态和溶液中均形成稳定的四聚体。基于序列分析和铜绿假单胞菌二氢嘧啶酶与Thermus sp。二聚体-二聚体界面的结构比较。二氢嘧啶酶，提出了不同的低聚机理。