Two apicoplast dwelling glycolytic enzymes provide key substrates for metabolic pathways in the apicoplast and are critical for Toxoplasma growth.
Two apicoplast dwelling glycolytic enzymes provide key substrates for metabolic pathways in the apicoplast and are critical for Toxoplasma growth.
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两种顶质体糖酵解酶为顶质体代谢途径提供关键底物，对弓形虫生长至关重要
DOI：
10.1371/journal.ppat.1011009
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发表时间：
2022-11
期刊：
影响因子：
6.7
通讯作者：
中科院分区：
文献类型：
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作者：
许多顶复合体寄生物都有一个非光合质体，称为顶质体，它承载着重要的代谢途径，如甲基红四醇4-磷酸（MEP）途径，合成类异戊二烯前体。然而，顶质体代谢的许多细节尚不清楚。在这项研究中，我们研究了四种糖酵解酶在刚地弓形虫顶质体中的生理作用。弓形虫体内的许多糖酵解酶有两个或更多的同工异构体。内源性标记这些酶发现其中四个定位于顶质体，包括丙酮酸激酶2 (PYK2)，磷酸甘油酸激酶2 (PGK2)，三磷酸异构酶2 （TPI2）和磷酸甘油醛脱氢酶2 （GAPDH2）。产生ATP的酶PYK2和PGK2被认为是顶质体的主要能量来源。令人惊讶的是，单独或同时删除PYK2和PGK2不会导致寄生虫生长或毒力的重大缺陷。相比之下，TPI2和GAPDH2对速殖子增殖至关重要。条件耗尽TPI2导致MEP途径中间体水平显著降低，导致寄生虫生长停滞。在TPI2缺失突变体中，另一种被称为甲羟戊酸途径的类异戊二烯前体合成途径的重建部分地挽救了其生长缺陷。同样，敲除产生NADPH的GAPDH2酶也通过MEP途径减少类异戊二烯前体合成，抑制寄生虫增殖。此外，它还减少了顶质体中脂肪酸的新合成。综上所述，这些数据提示了一个模型，即居住在顶质体中的TPI2为类异戊二烯前体的合成提供了碳源，而GAPDH2则为弓形虫的MEP、脂肪酸合成和铁氧还蛋白氧化还原系统等途径提供了还原能力。因此，这两种酶对寄生虫生长至关重要，并可作为抗弓形虫干预设计的潜在靶点。另一方面，PYK2和PGK2的可有可无表明顶质体中有其他能量来源，值得进一步研究。
Many apicomplexan parasites harbor a non-photosynthetic plastid called the apicoplast, which hosts important metabolic pathways like the methylerythritol 4-phosphate (MEP) pathway that synthesizes isoprenoid precursors. Yet many details in apicoplast metabolism are not well understood. In this study, we examined the physiological roles of four glycolytic enzymes in the apicoplast of Toxoplasma gondii. Many glycolytic enzymes in T. gondii have two or more isoforms. Endogenous tagging each of these enzymes found that four of them were localized to the apicoplast, including pyruvate kinase2 (PYK2), phosphoglycerate kinase 2 (PGK2), triosephosphate isomerase 2 (TPI2) and phosphoglyceraldehyde dehydrogenase 2 (GAPDH2). The ATP generating enzymes PYK2 and PGK2 were thought to be the main energy source of the apicoplast. Surprisingly, deleting PYK2 and PGK2 individually or simultaneously did not cause major defects on parasite growth or virulence. In contrast, TPI2 and GAPDH2 are critical for tachyzoite proliferation. Conditional depletion of TPI2 caused significant reduction in the levels of MEP pathway intermediates and led to parasite growth arrest. Reconstitution of another isoprenoid precursor synthesis pathway called the mevalonate pathway in the TPI2 depletion mutant partially rescued its growth defects. Similarly, knocking down the GAPDH2 enzyme that produces NADPH also reduced isoprenoid precursor synthesis through the MEP pathway and inhibited parasite proliferation. In addition, it reduced de novo fatty acid synthesis in the apicoplast. Together, these data suggest a model that the apicoplast dwelling TPI2 provides carbon source for the synthesis of isoprenoid precursor, whereas GAPDH2 supplies reducing power for pathways like MEP, fatty acid synthesis and ferredoxin redox system in T. gondii. As such, both enzymes are critical for parasite growth and serve as potential targets for anti-toxoplasmic intervention designs. On the other hand, the dispensability of PYK2 and PGK2 suggest additional sources for energy in the apicoplast, which deserves further investigation.
影响因子：
1.9
作者：
Maeda T;Saito T;Harb OS;Roos DS;Takeo S;Suzuki H;Tsuboi T;Takeuchi T;Asai T
通讯作者：
Asai T
影响因子：
6.7
作者：
通讯作者：
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