DcsB, one of the enzymes encoded in the d‐cycloserine (d‐CS) biosynthetic gene cluster, displays a high sequence homology to arginase, which contains two manganese ions in the active site. However, DcsB hydrolyzes N^ω‐hydroxy‐l‐arginine, but not l‐arginine, to supply hydroxyurea for the biosynthesis of d‐CS. Here, the crystal structure of DcsB was determined at a resolution of 1.5 Å using anomalous scattering from the manganese ions. In the crystal structure, DscB generates an artificial dimer created by the open and closed forms. Gel‐filtration analysis demonstrated that DcsB is a monomeric protein, unlike arginase, which forms a trimeric structure. The active center containing the binuclear manganese cluster differs between DcsB and arginase. In DcsB, one of the ligands of the Mn_A ion is a cysteine, while the corresponding residue in arginase is a histidine. In addition, DcsB has no counterpart to the histidine residue that acts as a general acid/base during the catalytic reaction of arginase. The present study demonstrates that DcsB has a unique active site that differs from that of arginase.

中文翻译：

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在D-环丝氨酸生物合成途径中发现的Nω-羟基-L-精氨酸水解酶的晶体结构。

DcsB是d-环丝氨酸（d- CS）生物合成基因簇中编码的酶之一，与精氨酸酶具有高度的序列同源性，精氨酸酶的活性位点中含有两个锰离子。然而，DcsB水解Ñ ^ω羟基升精氨酸，但不是升精氨酸，以供应为羟基脲的生物合成d‐CS。此处，使用来自锰离子的异常散射，以1.5的分辨率确定了DcsB的晶体结构。在晶体结构中，DscB生成由开放和封闭形式产生的人工二聚体。凝胶过滤分析表明，DcsB是一种单体蛋白，与精氨酸酶不同，后者形成三聚体结构。DcsB和精氨酸酶的活性中心包含双核锰簇。在DcsB中，Mn _A离子的配体之一是半胱氨酸，而精氨酸酶中的相应残基是组氨酸。另外，DcsB与在精氨酸酶催化反应期间充当一般酸/碱的组氨酸残基没有对应物。本研究表明，DcsB具有一个独特的活性位点，不同于精氨酸酶。