Plant d-2-Hydroxyglutarate Dehydrogenase Participates in the Catabolism of Lysine Especially during Senescence

Abstract

D-2-Hydroxyglutarate dehydrogenase (D-2HGDH) catalyzes the specific and efficient oxidation of D-2-hydroxyglutarate (D-2HG) to 2-oxoglutarate using FAD as a cofactor. In this work, we demonstrate that D-2HGDH localizes to plant mitochondria and that its expression increases gradually during developmental and dark-induced senescence in Arabidopsis thaliana, indicating an enhanced demand of respiration of alternative substrates through this enzymatic system under these conditions. Using loss-of-function mutants in D-2HGDH (d2hgdh1) and stable isotope dilution LC-MS/MS, we found that the D-isomer of 2HG accumulated in leaves of d2hgdh1 during both forms of carbon starvation. In addition to this, d2hgdh1 presented enhanced levels of most TCA cycle intermediates and free amino acids. In contrast to the deleterious effects caused by a deficiency in D-2HGDH in humans, d2hgdh1 and overexpressing lines of D-2HGDH showed normal developmental and senescence phenotypes, indicating a mild role of D-2HGDH in the tested conditions. Moreover, metabolic fingerprinting of leaves of plants grown in media supplemented with putative precursors indicated that D-2HG most probably originates during the catabolism of lysine. Finally, the L-isomer of 2HG was also detected in leaf extracts, indicating that both chiral forms of 2HG participate in plant metabolism. 2-Hydroxyglutarate (2HG3 ; 2-hydroxypentanedioic acid) is a five-carbon dicarboxylic acid with the hydroxy group on the ␣-carbon. D-2HG accumulates in humans in the inherited neurometabolic disorder 2-hydroxyglutaric aciduria (2HGA) due to a deficiency in D-2HG dehydrogenase (D-2HGDH) (1), which converts D-2HG to 2-oxoglutarate (2OG); the electron transfer flavoprotein (ETF); or the ETF-ubiquinone oxidoreductase (ETFQO) (2), both electron acceptors of D-2HGDH (1). The clinical symptoms encompass developmental retardation, neurological dysfunction, and cerebral atrophy (1). In addition to high levels of 2HG, patients with 2HGA also have high concentrations of TCA cycle intermediates. On the other hand, excess accumulation of D-2HG contributes to the formation and malignant progression of brain tumors (3). Mutations in the cytosolic enzyme IDH1 (isocitrate dehydrogenase 1) occur in ϳ80% of secondary brain cancer tumors and in nearly onetenth of acute myelogenous leukemia tumors. Normally, IDH1 catalyzes the conversion of isocitrate to 2OG. Cancer-associated mutations in IDH1 reduce the affinity of the enzyme for isocitrate and increase the affinity for NADPH and 2OG. This prevents the oxidative decarboxylation of isocitrate to 2OG and facilitates the conversion of 2OG to D-2HG. In this way, IDH1 mutations cause a gain of function, resulting in the production and accumulation of D-2HG (3).D-2HG occurs in mammals (i) in the conversion of 2OG to D-2HG through a hydroxy acid-oxoacid transhydrogenase with the concomitant conversion of ␥-hydroxybutyrate to succinic semialdehyde (4), (ii) as an intermediate in the succinate-glycine cycle between 2OG semialdehyde and 2OG (5), and (iii) in ...

Analysis of a Range of Catabolic Mutants Provides Evidence That Phytanoyl-Coenzyme A Does Not Act as a Substrate of the Electron-Transfer Flavoprotein/Electron-Transfer Flavoprotein:Ubiquinone Oxidoreductase Complex in Arabidopsis during Dark-Induced Senescence

“…We were additionally able to ascertain that isovaleryl-CoA dehydrogenase was involved in degradation of the branched-chain amino acids, phytol, and Lys while in contrast 2-hydroxyglutarate dehydrogenase was exclusively involved in Lys degradation (Araú jo et al, 2010). In agreement with this, it has been recently demonstrated that this alternative pathway and particularly 2-hydroxyglutarate dehydrogenase, is operational during the dark period in Arabidopsis grown under regular diurnal light cycles and indicated Lys as the most suitable substrate generating 2-hydroxyglutarate in plants (Engqvist et al, 2011).…”

GLYCOLATE OXIDASE3, a Glycolate Oxidase Homolog of Yeast l-Lactate Cytochrome c Oxidoreductase, Supports l-Lactate Oxidation in Roots of Arabidopsis

“…D-2-Hydroxyglutarate derives from Lys, especially in conditions of higher protein catabolism, and is oxidized in plant mitochondria to 2-ketoglutarate through D-2-hydroxyglutarate dehydrogenase (Engqvist et al, 2009(Engqvist et al, , 2011Araújo et al, 2010;Kuhn et al, 2013). The increased amounts of 2-hydroxyglutarate observed in wild-type and gox3-1 plants under hypoxia suggest an enhanced protein turnover under this condition.…”

“…Interestingly, the amount of 2-hydroxyglutarate, a tricarboxylic acid cycle-related metabolite (Araujo et al, 2010;Engqvist et al, 2011Engqvist et al, , 2014, increased significantly during hypoxia. In gox3-1, the level of 2-hydroxyglutarate already accumulated at 8 h of hypoxia.…”

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“…2-Hydroxyglutarate is known to participate in butanoate metabolism and is involved in lysine and aromatic amino acid catabolic pathways that can be used under certain circumstances to support mitochondrial respiration (Engqvist et al, 2011). 2-Aminoadipate is also involved in the lysine degradation pathway as a pipecolate catabolite (Goyer et al, 2004).…”