Enzymic properties and capacities of developing tomato (Lycopersicon esculentum L.) fruit plastids |
| |
Authors: | Buker M; Schunemann D; Borchert S |
| |
Institution: | Institut fur Biochemie der Pflanze, Universitat Gottingen, Untere Karspule, D-37073 Gottingen, Germany; Corresponding author; e-mail: mbueker@gwdg.de |
| |
Abstract: | To characterize the developmental stage of tomato fruits, chlorophyll
content, photosynthetic O2 evolution and CO2 fixation of pericarp slices
were determined. During the first developmental stages a higher expression
level of the triose phosphate translocator was detected. Transport
measurements revealed that both the hexose phosphate and the triose
phosphate translocator are very likely to be active at this time. Plastidic
and cytosolic fructose-1,6-bisphosphatase are active in green fruit
pericarp, whereas in red pericarp only the cytosolic form is present.
Tomato fruit chloroplasts are able to synthesize starch from Glc6P. Starch
synthesis is strongly dependent on the addition of 3PGA and ATP and on
plastid illumination. Fruit chloroplasts exhibit very low CO2 fixation
rates and so the capacities of green pericarp slices were investigated. In
relation to chlorophyll content, pericarp slices show the same capacity of
starch synthesis as spinach or potato leaves. To investigate the presence
of further reactions consuming the products of photosynthetic electron
transport, the GOGAT activity was measured. In the light,
glutamine/2-oxoglutarate-dependent formation of glutamate occurred with a
high activity. In the presence of Glc6P only 18% of the light activity was
obtained. Since the Glc6P-dependent activity is rather low, the release of
14CO2 from labelled
1-14C]-Glc6P was also measured. In the dark, the
formation of glutamate and oxidation of Glc6P are very tightly coupled to
each other in fruit chloroplasts. |
| |
Keywords: | |
本文献已被 Oxford 等数据库收录! |
|