Key Laboratory of Nutrition and Metabolism, Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.
School of Life Sciences, Lanzhou University, Lanzhou 730000, China.
Biosci Rep. 2018 Jan 17;38(1). doi: 10.1042/BSR20171617. Print 2018 Feb 28.
Urea is the degradation product of a wide range of nitrogen containing bio-molecules. Urea amidolyase (UA) catalyzes the conversion of urea to ammonium, the essential first step in utilizing urea as a nitrogen source. It is widely distributed in fungi, bacteria and other microorganisms, and plays an important role in nitrogen recycling in the biosphere. UA is composed of urea carboxylase (UC) and allophanate hydrolase (AH) domains, which catalyze sequential reactions. In some organisms UC and AH are encoded by separated genes. We present here structure of the (KlUA). The structure revealed that KlUA forms a compact homo-dimer with a molecular weight of 400 kDa. Structure inspired biochemical experiments revealed the mechanism of its reaction intermediate translocation, and that the KlUA holo-enzyme formation is essential for its optimal activity. Interestingly, previous studies and ours suggest that UC and AH encoded by separated genes probably do not form a KlUA-like complex, consequently they might not catalyze the urea to ammonium conversion as efficiently.
尿素是广泛存在于含氮生物分子中的降解产物。尿素酰胺酶（UA）能够催化尿素转化为铵，这是利用尿素作为氮源的关键的第一步。它广泛存在于真菌、细菌和其他微生物中，在生物圈内的氮循环中起着重要作用。UA 由尿素羧化酶（UC）和异丁烯酸水解酶（AH）结构域组成，它们催化连续的反应。在一些生物中，UC 和 AH 是由独立的基因编码的。我们在此展示了 KlUA 的结构。该结构揭示了 KlUA 形成一个分子量为 400 kDa 的紧凑同型二聚体。受结构启发的生化实验揭示了其反应中间产物转移的机制，并且 KlUA 全酶的形成对于其最佳活性是必需的。有趣的是，先前的研究和我们的研究表明，由独立基因编码的 UC 和 AH 可能不会形成类似 KlUA 的复合物，因此它们可能不会有效地催化尿素向铵的转化。
