The involvement of glutamate dehydrogenase in the adaptation of mitochondria to oxidize glutamate in sucrose starved pea embryos |
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Authors: | I Morkunas T Lehmann W Ratajczak L Ratajczak B Tomaszewska |
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Institution: | (1) Department of Experimental Biology WSP Słupsk, ul. Arciszewskiego 22b;(2) Department of Plant Physiology UAM Poznań, Al. Niepodległości 14;(3) Department of Plant Metabolism UAM Poznań, ul. Fredry 10 |
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Abstract: | Embryos of pea (Pisum sativum L. cv Sol) deprived of cotyledons were cultured for 3 days in medium with or without sucrose. Respiratory activity of embryos (intact)
as well as the ability to oxidize glutamate by mitochondria isolated from embryos were studied. Respiration of intact embryos
grown in sucrose supplemented medium was more intensive than in the starved ones. Transfer of the starved embryos to the sucrose-containing
medium induced the increase in the intensity of O2 consumption. Mitochondria isolated from both starved and control embryos exhibited respiratory control. Mitochondria isolated
from embryos cultured in the absence of sucrose showed higher (about 60 %) ability to oxidize glutamate and α-ketoglutarate
than mitochondria from embryos grown in sucrose containing medium. The absence of sucrose in the medium led to a rapid increase
in the specific activity of glutamate dehydrogenase (NADH-GDH and NAD-GDH) and it was accompanied by changes in izoenzymatic
pattern of enzyme. These results suggest that in the conditions of sucrose starvation glutamate dehydrogenase may be responsible
for the increase of glutamate oxidation by mitochondria of pea embryos. Electrophoretic separation of glutamate dehydrogenase
isolated from embryos cultured in medium without sucrose showed the presence of ca. 17 isoenzymes while in non-starved embryos only 7 isoenzymes were identified. However, the addition of sucrose to starved
embryos after 24 hours of cultivation led to a decrease in glutamate dehydrogenase activity (up to 40 %) but it did not cause
the changes in isoenzymatic pattern. These results suggest that in the conditions of sucrose starvation glutamate dehydrogenase
maybe responsible for the increase of glutamate oxidation by mitochondria of pea embryos. The posibility of glutamate dehydrogenase
regulation by sucrose is discussed. |
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