Mycobacterium tuberculosis appears to lack alpha-ketoglutarate dehydrogenase and encodes pyruvate dehydrogenase in widely separated genes. Mol Microbiol

Department of Microbiology and Immunology, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA.
Molecular Microbiology (Impact Factor: 4.42). 09/2005; 57(3):859-68. DOI: 10.1111/j.1365-2958.2005.04741.x
Source: PubMed


Mycobacterium tuberculosis (Mtb) persists for prolonged periods in macrophages, where it must adapt to metabolic limitations and oxidative/nitrosative stress. However, little is known about Mtb's intermediary metabolism or antioxidant defences. We recently identified a peroxynitrite reductase-peroxidase complex in Mtb that included products of the genes sucB and lpd, which are annotated to encode the dihydrolipoamide succinyltransferase (E2) and lipoamide dehydrogenase (E3) components of alpha-ketoglutarate dehydrogenase (KDH). However, we could detect no KDH activity in Mtb lysates, nor could we reconstitute KDH by combining the recombinant proteins SucA (annotated as the E1 component of KDH), SucB and Lpd. We therefore renamed the sucB product dihydrolipoamide acyltransferase (DlaT). Mtb lysates contained pyruvate dehydrogenase (PDH) activity, which was lost when the dlaT gene (formerly, sucB) was disrupted. Purification of PDH from Mtb yielded AceE, annotated as an E1 component of PDH, along with DlaT and Lpd. Moreover, anti-DlaT antibody coimmunoprecipitated AceE. Finally, recombinant AceE, DlaT and Lpd, although encoded by genes that are widely separated on the chromosome, reconstituted PDH in vitro with Km values typical of bacterial PDH complexes. In sum, Mtb appears to lack KDH. Instead, DlaT and Lpd join with AceE to constitute PDH.

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Available from: Hediye Erdjument-Bromage, Sep 17, 2014
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    • "For example, this metabolite has been shown to inhibit pyruvate dehydrogenase (PDH) and citrate synthase in other bacteria (Brock and Buckel, 2004; Man et al., 1995; Maruyama and Kitamura, 1985). While the accumulation of glycolytic intermediates we observed in cholesterol-grown mycobacteria could be consistent with the these mechanisms, it is unclear whether the unusual PDH complex (Tian et al., 2005), or the apparently redundant citrate synthase enzymes (CitA and GltA) of mycobacteria are inhibited by propionyl-CoA. Similarly, propionate-related toxicity in MCC-deficient Salmonella is due to the accumulation of a specific 2- methylcitrate isomer, which inhibits the gluconeogenic enzyme, fructose 1,6 bisphosphatase (Rocco and Escalante-Semerena). "
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    ABSTRACT: To understand the adaptation of Mycobacterium tuberculosis to the intracellular environment, we used comprehensive metabolite profiling to identify the biochemical pathways utilized during growth on cholesterol, a critical carbon source during chronic infection. Metabolic alterations observed during cholesterol catabolism centered on propionyl-CoA and pyruvate pools. Consequently, growth on this substrate required the transcriptional induction of the propionyl-CoA-assimilating methylcitrate cycle (MCC) enzymes, via the Rv1129c regulatory protein. We show that both Rv1129c and the MCC enzymes are required for intracellular growth in macrophages and that the growth defect of MCC mutants is largely attributable to the degradation of host-derived cholesterol. Together, these observations define a coordinated transcriptional and metabolic adaptation that is required for scavenging carbon during intracellular growth.
    Chemistry & biology 02/2012; 19(2):218-27. DOI:10.1016/j.chembiol.2011.12.016 · 6.65 Impact Factor
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    • "Oxidized AhpD is regenerated by dihydrolipoamide acyltransferase (DlaT); in turn, dihydrolipoamide dehydrogenase (Lpd) mediates the reduction of DlaT at NADH expense and completes the catalytic cycle (Bryk et al., 2002). dlaT (Rv2215) encodes the E2 component of the piruvate deshydrogenase complex, and lpdC (Rv0462), the only functional Lpd in M. tuberculosis (Argyrou & Blanchard, 2001), most probably codifies the E3 components of the piruvate deshydrogenase complex (Tian et al., 2005). Secondly, thioredoxin C (TrxC), but not thioredoxin B (TrxB) or A (TrxA), was also able to act as AhpC reducing substrates (Jaeger et al., 2004), and the catalytic cycle is completed by thioredoxin reductase (MtTR) and NADPH. "
    Understanding Tuberculosis - Deciphering the Secret Life of the Bacilli, 02/2012; , ISBN: 978-953-307-946-2
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    • "(Rv1248c), as annotated in databases and used by Tian et al. (2005b) "
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    ABSTRACT: The α-ketoglutarate dehydrogenase (KDH) complex is a major regulatory point of aerobic energy metabolism. Mycobacterium tuberculosis was reported to lack KDH activity, and the putative KDH E1o component, α-ketoglutarate decarboxylase (KGD), was instead assigned as a decarboxylase or carboligase. Here, we show that this protein does in fact sustain KDH activity, as well as the additional two reactions, and these multifunctional properties are shared by the Escherichia coli homolog, SucA. We also show that the mycobacterial enzyme is finely regulated by an additional acyltransferase-like domain and by the action of acetyl-CoA, a powerful allosteric activator able to enhance the concerted protein motions observed during catalysis. Our results uncover the functional plasticity of a crucial node in bacterial metabolism, which may be important for M. tuberculosis during host infection.
    Chemistry & biology 08/2011; 18(8):1011-20. DOI:10.1016/j.chembiol.2011.06.004 · 6.65 Impact Factor
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