D-Lactate Dehydrogenase Links Methylglyoxal Degradation and Electron Transport through Cytochrome c  . Issue 2 (9th August 2016)

• Record Type: Journal Article
• Authors: Welchen, Elina; Schmitz, Jessica; Fuchs, Philippe; García, Lucila; Wagner, Stephan; Wienstroer, Judith; Schertl, Peter; Braun, Hans-Peter; Schwarzländer, Markus; Gonzalez, Daniel H.; Maurino, Veronica G.
• Is Part Of: Plant physiology. Volume 172:Issue 2(2016)
• Page Start: 901
• Page End: 912
• Publication Date: 2016-08-09
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.16.01174
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : Mitochondrial d -lactate dehydrogenase links the last step of methylglyoxal detoxification to the mitochondrial electron transport chain through cytochrome c. Abstract: Glycolysis generates methylglyoxal (MGO ) as an unavoidable, cytotoxic by-product in plant cells. MGO scavenging is performed by the glyoxalase system, which produces d -lactate as an end product. d -Lactate dehydrogenase (d -LDH) is encoded by a single gene in Arabidopsis ( Arabidopsis thaliana ; At5g06580). It catalyzes in vitro the oxidation of d -lactate to pyruvate using flavin adenine dinucleotide as a cofactor; knowledge of its function in the context of the plant cell remains sketchy. Blue native-polyacrylamide gel electrophoresis of mitochondrial extracts combined with in gel activity assays using different substrates and tandem mass spectrometry allowed us to definitely show that d -LDH acts specifically on d -lactate, is active as a dimer, and does not associate with respiratory supercomplexes of the inner mitochondrial membrane. The combined use of cytochrome c (CYT c ) loss-of-function mutants and respiratory complex III inhibitors showed that CYT c acts as the in vivo electron acceptor of d -LDH. CYT c loss-of-function mutants, as well as the d -LDH mutants, were more sensitive to d -lactate and MGO, indicating that they function in the same pathway. In addition, overexpression of d -LDH and CYT c increased tolerance to d -lactate and MGO . Together with fine-localization of d -LDH, the functional interaction with CYT c in vivo strongly suggests that d -lactate oxidation takes place in the mitochondrial intermembrane space, delivering electrons to the respiratory chain through CYT c . These results provide a comprehensive picture of the organization and function of d -LDH in the plant cell and exemplify how the plant mitochondrial respiratory chain can act as a multifunctional electron sink for reductant from cytosolic pathways.