caa a22 4500 477101925 CHVBK 20180405111544.0 cr unu---uuuuu 170330e19960601xx s 000 0 eng 10.1007/BF00196575 doi (NATIONALLICENCE)springer-10.1007/BF00196575 Metabolism of glucose-6-phosphate and utilization of multiple metabolites for fatty acid synthesis by plastids from developing oilseed rape embryos [Elektronische Daten] [Fan Kang, Stephen Rawsthorne] The aim of this work was to investigate the partitioning of imported glucose 6-phosphate (Glc6P) to starch and fatty acids, and to CO2 via the oxidative pentose phosphate pathway (OPPP) in plastids isolated from developing embryos of oilseed rape (Brassica napus L.). The ability of the isolated plastids to utilize concurrently supplied substrates and the effects of these substrate combinations on the Glc6P partitioning were also assessed. The relative fluxes of carbon from Glc6P to starch, fatty acids, and to CO2 via the OPPP were close to 2∶1∶1 when Glc6P was supplied alone. Under these conditions NADPH generated via the OPPP was greater than that required by the concurrent rate of fatty acid synthesis. Fatty acid synthesis was unaffected by the presence or absence of exogenous NADH and/or NADPH and the requirement of fatty acid synthesis for reducing power is therefore met entirely by intraplastidial metabolism. When Glc6P was supplied in the presence of either pyruvate or pyruvate and acetate, the total flux from these metabolites to fatty acids was up to threefold greater than that from either Glc6P or pyruvate when they were supplied singly. In these experiments there was little competition between Glc6P and pyruvate in fatty acid synthesis and the flux to starch was unchanged. This implies that the starch and fatty acid biosynthesis pathways did not compete for the exogenously supplied ATP on which they were strongly dependent. When Glc6P and pyruvate were provided together, the NADPH generated by the OPPP pathway was less than that required by the concurrent rate of fatty acid synthesis. This suggests that the metabolism of exogenous Glc6P via the OPPP can contribute to the NADPH demand created during fatty acid synthesis but it also indicates that other intraplastidial sources of reducing power must be available under the in-vitro conditions used. Springer-Verlag, 1996 Brassica nationallicence Embryo nationallicence Carbon partitioning nationallicence Fatty acid synthesis nationallicence Plastid nationallicence Starch synthesis nationallicence GAPDH : glyceraldehyde-3-phosphate dehydrogenase nationallicence Glc6P : glucose-6-phosphate nationallicence OPPP : oxidative pentose phosphate pathway nationallicence PIM : plastid isolation medium nationallicence Pyr : pyruvate nationallicence Kang Fan Brassica and Oilseeds Research Department, John Innes Centre, NR4 7UH, Colney, Norwich, UK aut Rawsthorne Stephen Brassica and Oilseeds Research Department, John Innes Centre, NR4 7UH, Colney, Norwich, UK aut Planta Springer-Verlag 199/2(1996-06-01), 321-327 0032-0935 199:2<321 1996 199 425 https://doi.org/10.1007/BF00196575 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00196575 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kang Fan Brassica and Oilseeds Research Department, John Innes Centre, NR4 7UH, Colney, Norwich, UK aut NATIONALLICENCE 700 1- Rawsthorne Stephen Brassica and Oilseeds Research Department, John Innes Centre, NR4 7UH, Colney, Norwich, UK aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/2(1996-06-01), 321-327 0032-0935 199:2<321 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer