Variant tricarboxylic acid cycle in Mycobacterium tuberculosis:: Identification of α-ketoglutarate decarboxylase
Variant tricarboxylic acid cycle in Mycobacterium tuberculosis:: Identification of α-ketoglutarate decarboxylase
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DOI：
10.1073/pnas.0501605102
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发表时间：
2005-07-26
影响因子：
11.1
通讯作者：
Nathan, C
中科院分区：
文献类型：
--
作者：
Tian, J;Bryk, R;Nathan, C
结核分枝杆菌（Mtb）已适应其代谢，以在人类巨噬细胞中持续存在。这些适应可能涉及结核分枝杆菌的核心中间代谢，其酶很少被研究。预期三羧酸循环产生能量、脂质、氨基酸和血红素的前体。Mtb H37 Rv的基因组序列预测存在完整的三羧酸循环，但我们最近发现Mtb裂解物中缺乏α-酮戊二酸脱氢酶（KDH）活性。在这里，我们表明，柠檬酸合酶，乌头酸酶，异柠檬酸脱氢酶，脱氢酶，苹果酸脱氢酶，琥珀酸脱氢酶，但不KDH，存在，提高了单独的氧化和还原半循环的可能性。作为半循环之间的潜在联系，我们发现Rv 1248 c，注释为编码SucA，KDH的推定El组分，而不是编码α-酮戊二酸脱羧酶（Kgd），并产生琥珀酸半醛。在Mtb裂解物中检测到琥珀酸半醛脱氢酶活性，并用重组蛋白GabD 1（由Rv 0234 c编码）和GabD 2（由Rv 1731编码）重现。Kgd和GabD 1或GabD 2形成从α-酮戊二酸到琥珀酸的替代途径。Rv 1248 c，其是Mtb正常生长所必需的或必需的[Sassetti，C.，博伊德，D。H. & Rubin，E. J.（2003）Mol. Microbiol 48，77-84]是显示编码Kgd的第一个基因。人类缺乏Kgd，可能是结核病化疗的潜在靶点。
Mycobacterium tuberculosis (Mtb) has adapted its metabolism for persistence in the human macrophage. The adaptations are likely to involve Mtb's core intermediary metabolism, whose enzymes have been little studied. The tricarboxylic acid cycle is expected to yield precursors for energy, lipids, amino acids, and heme. The genome sequence of Mtb H37Rv predicts the presence of a complete tricarboxylic acid cycle, but we recently found that a-ketoglutarate dehydrogenase (KDH) activity is lacking in Mtb lysates. Here we showed that citrate synthase, aconitase, isocitrate dehydrogenase, fumarase, malate dehydrogenase, and succinate dehydrogenase, but not KDH, are present, raising the possibility of separate oxidative and reductive half-cycles. As a potential link between the half-cycles, we found that Rv1248c, annotated as encoding SucA, the putative El component of KDH, instead encodes a-ketoglutarate decarboxylase (Kgd) and produces succinic semialdehyde. Succinic semialdehyde dehydrogenase activity was detected in Mtb lysates and recapitulated with recombinant proteins GabD1 (encoded by Rv0234c) and GabD2 (encoded by Rv1731). Kgd and GabD1 or GabD2 form an alternative pathway from alpha-ketoglutarate to succinate. Rv1248c, which is essential or required for normal growth of Mtb [Sassetti, C., Boyd, D. H. & Rubin, E. J. (2003)Mol. Microbiol 48, 77-84] is the first gene shown to encode a Kgd. Kgd is lacking in humans and may represent a potential target for chemotherapy of tuberculosis.