| | 1 | Author
| M. Anfred Steingraber, Hanns Frohnm, Rüdiger Ham | Requires cookie* | | | Title
| Light-Dependent Sucrose Synthesis in Cell-Free (Reconstituted) Lysates of Evacuolated Mesophyll Protoplasts  | | | | Abstract
| Oat mesophyll protoplasts were evacuolated by centrifugation on a Percoll gradient and used as starting material for establishing a functional cell-free system. For this purpose evacuolated protoplasts were osm otically lysed. From the resulting homogenate a cytosolic fraction was obtained by silicon oil filtration. This fraction was used to dilute preparations o f lysed evacu olated protoplasts in order to reduce the number o f organelles per volume cytosol. The latter was necessary to increase light-dependent oxygen evolution o f the cell-free system. The result ing kind o f "reconstituted" system showed light-dependent sucrose formation (about 100 nmol (mg Chi)-1 • h r 1) with bicarbonate as the only substrate. As this property depends on a functional interaction o f chloroplast and cytosolic reactions, this cell-free system appeared to perform essential steps o f partitioning o f C 0 2 between starch and sucrose. Addition o f about 12 (im fructose 2 ,6 -bisphosphate, an inhibitor o f fructose 1,6 -bisphosphatase and an activator o f the PPi-dependent fructose 6 -phosphate phosphotransferase, caused sucrose degradation in the light. Thus, this cell-free system allows both the study o f cytosolic enzyme activities under quasi in vivo conditions and the manipulation o f cellular reaction sequences by plasma mem brane-impermeable compounds. | | | |
Reference
| Z. Naturforsch. 45c, 217 (1990); received January 11 1990 | | | |
Published
| 1990 | | | |
Keywords
| Avena sativa, Cell-Free System, Evacuolation, Mesophyll Protoplasts, Sucrose Synthesis | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0217.pdf | | | | Identifier
| ZNC-1990-45c-0217 | | | | Volume
| 45 | |
| 2 | Author
| Mark Stitt, G. Ottfried, M. Ieskes+, H. Ans-D, HeikeG. Ieter Söling+, Roße, HansW. Heidt | Requires cookie* | | | Title
| Diurnal Changes of Fructose-6-phosphate,2-kinase and Fructose-2,6-bis-phosphatase Activities in Spinach Leaves | | | | Abstract
| Extracts have been rapidly prepared from spinach leaves, and the activity of fructose-6-phos-phate,2-kinase (Fru6P,2kinase) and fructose-2,6-bisphosphatase (Fru2.6P:ase) measured. The enzym e activities do not change during light-dark transitions, but there is an increase of Fru6P,2-kinase and decrease o f Fru2,6P2ase activity over several hours in the light. This increase of the Fru6P,2kinase: Fru2,6P:ase ratio shows that a previously unrecognized mechanism , which may include protein m odification, controls Fru2,6P2 levels in leaves. It operates as sucrose accumu lates in the leaf, and will be involved in regulating the partitioning o f photosynthate. | | | |
Reference
| Z. Naturforsch. 41c, 291—296 (1986); received N ovem ber 25 1985 | | | |
Published
| 1986 | | | |
Keywords
| Fructose-2, 6-bisphosphate, Fructose-6-phosphate, 2-kinase, Fructose-2, 6-bisphosphatase, Photo synthesis, Sucrose Synthesis | | | |
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| default:Reihe_C/41/ZNC-1986-41c-0291.pdf | | | | Identifier
| ZNC-1986-41c-0291 | | | | Volume
| 41 | |
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