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

authored by
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 Km for pyruvate and the Ki 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.

Organisation(s)
Institute of Botany
Institute of Plant Genetics
Type
Article
Journal
PHYTOCHEMISTRY
Volume
95
Pages
168-176
No. of pages
9
ISSN
0031-9422
Publication date
02.08.2013
Publication status
Published
Peer reviewed
Yes
ASJC Scopus subject areas
Biochemistry, Molecular Biology, Plant Science, Horticulture
Electronic version(s)
https://doi.org/10.1016/j.phytochem.2013.07.009 (Access: Unknown)