Mobley H L, Hausinger R P
Microbiol Rev. 1989 Mar;53(1):85-108. doi: 10.1128/mr.53.1.85-108.1989.
Microbial ureases hydrolyze urea to ammonia and carbon dioxide. Urease activity of an infectious microorganism can contribute to the development of urinary stones, pyelonephritis, gastric ulceration, and other diseases. In contrast to these harmful effects, urease activity of ruminal and gastrointestinal microorganisms can benefit both the microbe and host by recycling (thereby conserving) urea nitrogen. Microbial ureases also play an important role in utilization of environmental nitrogenous compounds and urea-based fertilizers. Urease is a high-molecular-weight, multimeric, nickel-containing enzyme. Its cytoplasmic location requires that urea enter the cell for utilization, and in some species energy-dependent urea uptake systems have been detected. Eucaryotic microorganisms possess a homopolymeric urease, analogous to the well-studied plant enzyme composed of six identical subunits. Gram-positive bacteria may also possess homopolymeric ureases, but the evidence for this is not conclusive. In contrast, ureases from gram-negative bacteria studied thus far clearly possess three distinct subunits with Mrs of 65,000 to 73,000 (alpha), 10,000 to 12,000 (beta), and 8,000 to 10,000 (gamma). Tightly bound nickel is present in all ureases and appears to participate in catalysis. Urease genes have been cloned from several species, and nickel-containing recombinant ureases have been characterized. Three structural genes are transcribed on a single messenger ribonucleic acid and translated in the order gamma, beta, and then alpha. In addition to these genes, several other peptides are encoded in the urease operon of some species. The roles for these other genes are not firmly established, but may involve regulation, urea transport, nickel transport, or nickel processing.
微生物脲酶可将尿素水解为氨和二氧化碳。感染性微生物的脲酶活性可能会导致尿路结石、肾盂肾炎、胃溃疡及其他疾病的发生。与这些有害作用相反，瘤胃和胃肠道微生物的脲酶活性可通过尿素氮的循环利用（从而实现保存）使微生物和宿主均受益。微生物脲酶在环境含氮化合物和尿素基肥料的利用中也发挥着重要作用。脲酶是一种高分子量的多聚体含镍酶。其位于细胞质内，这就要求尿素进入细胞才能被利用，并且在某些物种中已检测到能量依赖型尿素摄取系统。真核微生物拥有一种同聚体脲酶，类似于已得到充分研究的由六个相同亚基组成的植物酶。革兰氏阳性菌也可能拥有同聚体脲酶，但这方面的证据并不确凿。相比之下，迄今为止所研究的革兰氏阴性菌的脲酶显然拥有三个不同的亚基，其分子量分别为65,000至73,000（α）、10,000至12,000（β）和8,000至10,000（γ）。所有脲酶中均存在紧密结合的镍，且似乎参与催化作用。脲酶基因已从多个物种中克隆出来，含镍重组脲酶也已得到表征。三个结构基因在单个信使核糖核酸上转录，并按γ、β、α的顺序进行翻译。除了这些基因外，某些物种的脲酶操纵子中还编码了其他几种肽。这些其他基因的作用尚未完全明确，但可能涉及调控、尿素转运、镍转运或镍加工。
