A possible role for the chloroplast pyruvate dehydrogenase complex in plant glycolate and glyoxylate metabolism

verfasst von

Christian Blume, Christof Behrens, Holger Eubel, Hans Peter Braun, Christoph Peterhänsel

Abstract

Glyoxylate is a peroxisomal intermediate of photorespiration, the recycling pathway for 2-phosphoglycolate (2-PG) produced by the oxygenase activity of Rubisco. Under hot and dry growth conditions, photorespiratory intermediates can accumulate and must be detoxified by alternative pathways, including plastidal reactions. Moreover, there is evidence that chloroplasts are capable of actively producing glyoxylate from glycolate. Further metabolic steps are unknown, but probably include a CO₂ release step. Here, we report that CO ₂ production from glycolate and glyoxylate in isolated tobacco chloroplasts can be inhibited by pyruvate, but not related compounds. We isolated a protein fraction that was enriched for the chloroplast pyruvate dehydrogenase complex (PDC). The fraction contained a protein complex of several MDa in size that included all predicted subunits of the chloroplast PDC and a so far unidentified HSP93-V/ClpC1 heat shock protein. Glyoxylate competitively inhibited NADH formation from pyruvate in this fraction. The K_m for pyruvate and the K_i for glyoxylate were 330 and 270 μM, respectively. Glyoxylate decarboxylation was also enriched in this fraction and could be in turn inhibited by pyruvate. Based on these data, we suggest that the chloroplast PDC might be part of a pathway for glycolate and/or glyoxylate oxidation in chloroplasts.

Organisationseinheit(en)

Institut für Botanik
Institut für Pflanzengenetik

Typ

Artikel

Journal

PHYTOCHEMISTRY

Band

95

Seiten

168-176

Anzahl der Seiten

9

ISSN

0031-9422

Publikationsdatum

02.08.2013

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Biochemie, Molekularbiologie, Pflanzenkunde, Gartenbau

Elektronische Version(en)

https://doi.org/10.1016/j.phytochem.2013.07.009 (Zugang: Unbekannt)