Leroux Alejandro E, Maugeri Dante A, Cazzulo Juan J, Nowicki Cristina
Instituto de Química y Fisicoquímica Biológica IQUIFIB-CONICET, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Buenos Aires, Argentina.
Mol Biochem Parasitol. 2011 May;177(1):61-4. doi: 10.1016/j.molbiopara.2011.01.010. Epub 2011 Feb 1.
Trypanosoma cruzi exhibits two putative isocitrate dehydrogenases (IDHs). Both idh genes were cloned and the recombinant enzymes expressed in Escherichia coli. Our results showed that T. cruzi IDHs are strictly dependent on NADP(+) and display apparent affinities towards isocitrate and the coenzyme in the low micromolar range. In T. cruzi, IDHs are cytosolic and mitochondrial enzymes, and there is no evidence for the typical Krebs cycle-related NAD-dependent IDH. Hence, like in Trypanosoma brucei, the Krebs cycle is not a canonical route in T. cruzi. However, the citrate produced in the mitochondrion could be isomerized into isocitrate in the cytosol and the mitochondrion by means of the putative aconitase, which would provide the substrate for both IDHs. The cytosolic IDH is significantly more abundant in amastigotes, cell-derived and metacyclic trypomastigotes than in epimastigotes. This observation fits in well with the expected oxidative burst this pathogen has to face when infecting the mammalian host.
克氏锥虫表现出两种假定的异柠檬酸脱氢酶（IDH）。两个idh基因均被克隆，并在大肠杆菌中表达了重组酶。我们的结果表明，克氏锥虫IDH严格依赖于NADP(+)，并对异柠檬酸和辅酶表现出低微摩尔范围内的表观亲和力。在克氏锥虫中，IDH是胞质和线粒体酶，没有证据表明存在与典型三羧酸循环相关的NAD依赖性IDH。因此，与布氏锥虫一样，三羧酸循环在克氏锥虫中不是一条典型途径。然而，线粒体中产生的柠檬酸可通过假定的乌头酸酶在胞质和线粒体中异构化为异柠檬酸，这将为两种IDH提供底物。胞质IDH在无鞭毛体、细胞来源的和循环后期锥鞭毛体中比在前鞭毛体中明显更丰富。这一观察结果与该病原体在感染哺乳动物宿主时必须面对的预期氧化爆发非常吻合。
