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

Erwin E.W. Jansen,Martin K.M. Engqvist,Judith Wienstroer,Anke Kuhn,Katrin Weber,Veronica G. Maurino,Andreas P.M. Weber,Cornelis Jakobs

doi:10.1074/jbc.m110.194175

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.

Highlights

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]
As gene coexpression analysis indicated that D-2HGDH is in the same network as several genes involved in ␤-oxidation and degradation of amino acids and chlorophyll, it was proposed that D-2HGDH participates in the catabolism of D-2HG most probably during the mobilization of alternative substrates from proteolysis and/or lipid degradation [11]

Summary

Introduction

2-Hydroxyglutarate (2HG3; 2-hydroxypentanedioic acid) is a five-carbon dicarboxylic acid with the hydroxy group on the ␣-carbon. 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.

Results

Conclusion