Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA 30602, USA.
Department of Cellular Biology, University of Georgia, Athens, GA 30602, U.S.A.
Biosci Rep. 2019 May 17;39(5). doi: 10.1042/BSR20190894. Print 2019 May 31.
, a protist parasite that causes African trypanosomiasis or sleeping sickness, relies mainly on glycolysis for ATP production when in its mammalian host. Glycolysis occurs within a peroxisome-like organelle named the glycosome. Previous work from our laboratory reported the presence of significant amounts of inorganic polyphosphate (polyP), a polymer of three to hundreds of orthophosphate units, in the glycosomes and nucleoli of In this work, we identified and characterized the activity of two Nudix hydrolases (NHs), Nudix hydrolase (TbNH) 2 and TbNH4, one located in the glycosomes and the other in the cytosol and nucleus, respectively, which can degrade polyP. We found that TbNH2 is an exopolyphosphatase with higher activity on short chain polyP, while TbNH4 is an endo- and exopolyphosphatase that has similar activity on polyP of various chain sizes. Both enzymes have higher activity at around pH 8.0. We also found that only TbNH2 can dephosphorylate ATP and ADP but with lower affinity than for polyP. Our results suggest that NHs can participate in polyP homeostasis and therefore may help control polyP levels in glycosomes, cytosol and nuclei of .
一种原生动物寄生虫，引起非洲锥虫病或昏睡病，当寄生在哺乳动物宿主中时，主要依赖糖酵解产生 ATP。糖酵解发生在一个被称为糖酵解体的过氧化物酶体样细胞器内。我们实验室之前的工作报道了无机多磷酸盐（polyP）的大量存在，polyP 是由三个到数百个正磷酸盐单元组成的聚合物，存在于糖酵解体和核仁中。在这项工作中，我们鉴定并表征了两种 Nudix 水解酶（NHs）的活性，即 Nudix 水解酶（TbNH）2 和 TbNH4，一种位于糖酵解体中，另一种分别位于细胞质和细胞核中，它们可以降解 polyP。我们发现 TbNH2 是一种外切多聚磷酸酶，对短链 polyP 的活性更高，而 TbNH4 是一种内切和外切多聚磷酸酶，对各种链长的 polyP 具有相似的活性。两种酶在 pH8.0 左右的活性较高。我们还发现只有 TbNH2 可以使 ATP 和 ADP 去磷酸化，但亲和力比 polyP 低。我们的结果表明，NHs 可以参与 polyP 的动态平衡，因此可能有助于控制糖酵解体、细胞质和细胞核中 polyP 的水平。
