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1990 (1)
1986 (1)
1Author    M. Anfred Steingraber, Hanns Frohnm, Rüdiger HamRequires 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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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0217.pdf 
 Identifier    ZNC-1990-45c-0217 
 Volume    45 
2Author    Mark Stitt, G. Ottfried, M. Ieskes+, H. Ans-D, HeikeG. Ieter Söling+, Roße, HansW. HeidtRequires 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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 TEI-XML for    default:Reihe_C/41/ZNC-1986-41c-0291.pdf 
 Identifier    ZNC-1986-41c-0291 
 Volume    41