Fatty-acid synthesis in chloroplasts from mustard (Sinapis alba L.) cotyledons: formation of acetyl coenzyme A by intraplastid glycolytic enzymes and a pyruvate dehydrogenase complex |
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Authors: | B Liedvogel R Bäuerle |
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Institution: | (1) Zellbiologie, Institut für Biologie II, Schänzlestrasse 1, D-7800 Freiburg, Federal Republic of Germany |
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Abstract: | Chloroplasts from the cotyledons of mustard (Sinapis alba L.) seedlings were isolated on Percoll gradients, and showed a high degree of intactness (92%) and purity as judged by electron microscopy and marker-enzyme analysis (cytoplasmic contamination lower than 0.4% on a protein basis). The chloroplasts synthesized longchain fatty acids from both precursors 1-14C] acetate and 2-14C]pyruvate; maximum incorporation rates were 96 nmol·(mg Chl)-1·h-1 for acetate and 213 nmol·(mg Chl)-1·h-1 for pyruvate. Acetyl-CoA-producing enzymatic activities, namely acetyl-CoA synthetase (EC 6.2.1.1.) and a pyruvate dehydrogenase complex, showed specific activities of 14.8 nmol·(mg protein)-1·min-1 and 18.2 nmol·(mg protein)-1·min-1, respectively. The glycolytic enzymes phosphoglyceromutase (EC 2.7.5.3) phosphopyruvate hydratase (EC 4.2.1.11) and pyruvate kinase (EC 2.7.1.40) were all found to be components of these chloroplasts, thus indicating a possible pathway for intraplastid acetyl-CoA formation.Abbreviations ACS
acetyl coenzyme A synthetase
- Chl
chlorophyll
- DTE
1,4-dithioerythritol
- PDHC
pyruvate dehydrogenase complex
- 3-PGA
3-phosphoglyceric acid |
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Keywords: | Acetyl coenzyme A synthetase Fatty acid synthesis (plastid) Glycolytic enzyme (plastid) Pyruvate dehydrogenase Sinapis (plastid fatty acid) |
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