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

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• 作者：Christian Blume ; Christof Behrens ; Holger Eubel ; Hans-Peter Braun ; Christoph Peterhansel
• 关键词：PDC ; pyruvate dehydrogenase complex ; TPP ; thiamine pyrophosphate ; 2D-BN/SDS&ndash ; PAGE ; two dimensional blue native SDS&ndash ; PAGE
• 刊名：Phytochemistry
• 出版年：2013
• 出版时间：November, 2013
• 年：2013
• 卷：95
• 期：Complete
• 页码：168-176
• 全文大小：1337 K

文摘

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 CO₂ 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 ¦ÌM, 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.