The virulence factor urease and its unexplored role in the metabolism of Cryptococcus neoformans.
The virulence factor urease and its unexplored role in the metabolism of Cryptococcus neoformans.
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毒力因子脲酶及其在新型隐球菌代谢中的未探索的作用。
DOI：
10.1093/femsyr/foaa031
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发表时间：
2020
影响因子：
3.2
通讯作者：
Botha,Alfred
中科院分区：
文献类型：
--
作者：
Toplis,Barbra;Bosch,Caylin;Schwartz,IlanS;Kenyon,Chris;Boekhout,Teun;Perfect,JohnR;Botha,Alfred
隐球菌尿素酶被认为对于酵母在其自然环境和人类宿主中遇到的外源尿素的降解是重要的。然而，由酵母自身代谢反应产生的内源性尿素也可以作为尿素酶的底物。使用野生型，尿素酶缺失突变体和尿素酶重组菌株的新型隐球菌H99，我们研究了反应位于上游和下游的内源性尿素。我们证明了脲酶对隐球菌的生长很重要，并且与26°C的营养丰富条件相比，37°C的营养有限条件下的脲酶活性更高。与具有功能性尿素酶的细胞相比，尿素酶缺陷细胞具有显著更高的细胞内尿素水平，并且还显示出更多的尿素酶活性，这可能作为内源性尿素的潜在来源。与尿素酶相关的代谢反应也受到影响，因为尿素酶阳性和尿素酶阴性细胞在胍丁胺酶活性、多胺合成以及细胞内脯氨酸和活性氧水平方面不同。最后，尿素酶缺陷细胞在26°C下显示出比野生型细胞更高的黑色素水平，而在37°C下观察到相反的情况。这些结果表明，隐球菌尿素酶与酵母细胞内的关键代谢途径的功能。
Cryptococcal urease is believed to be important for the degradation of exogenous urea that the yeast encounters both in its natural environment and within the human host. Endogenous urea produced by the yeast's own metabolic reactions, however, may also serve as a substrate for the urease enzyme. Using wild-type, urease-deletion mutant and urease-reconstituted strains ofCryptococcus neoformansH99, we studied reactions located up- and downstream from endogenous urea. We demonstrated that urease is important for cryptococcal growth and that, compared to nutrient-rich conditions at 26°C, urease activity is higher under nutrient-limited conditions at 37°C. Compared to cells with a functional urease enzyme, urease-deficient cells had significantly higher intracellular urea levels and also showed more arginase activity, which may act as a potential source of endogenous urea. Metabolic reactions linked to arginase were also affected, since urease-positive and urease-negative cells differed with respect to agmatinase activity, polyamine synthesis, and intracellular levels of proline and reactive oxygen species. Lastly, urease-deficient cells showed higher melanin levels at 26°C than wild-type cells, while the inverse was observed at 37°C. These results suggest that cryptococcal urease is associated with the functioning of key metabolic pathways within the yeast cell.
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