Succinic acid dehydrogenase plant

Researchers have reported that under anaerobic conditions, the oxidation of phosphoric acid in the mitochondria of plants became weakened and reduction potential increased. That means the ratio of NADH and NAD-r increased and ADP transformed to ATP. This caused the dehydrogenation activity of succinic semialdehyde dehydrogenase to decrease, and resulted in weakening the reaction of succinic semialdehyde dehydrogenase to form succinate this is beneficial to the accumulation of GABA in tea leaves. Sawai et al. further reported that the amount of... 

Freebaim noted a decrease in oxygen uptake of plant and bovine liver mitochondria that was reversible by glutathione and ascorbic acid. The activity of some mitochondrial enzymes, including succinic dehydrogenase and cytochrome oxidase, has been found to be susceptible to ozone. 

The formation of acetyl-CoA from pyruvate in animals is via the pyruvate dehydrogenase complex, which catalyzes the irreversible decarboxylation reaction. Carbohydrate is synthesized from oxaloacetate, which in turn is synthesized from pyruvate via pyruvate carboxylase. Since the pyruvate dehydrogenase reaction is irreversible, acetyl-CoA cannot be converted to pyruvate, and hence animals cannot realize a net gain of carbohydrate from acetyl-CoA. Because plants have a glyoxylate cycle and animals do not, plants synthesize one molecule of succinate and one molecule of malate from two molecules of acetyl-CoA and one of oxaloacetate. The malate is converted to oxaloacetate, which reacts with another molecule of acetyl-CoA and thereby continues the reactions of the glyoxylate cycle. The succinate is also converted to oxaloacetate via the enzymes of the citric acid cycle. Thus, one molecule of oxaloacetate is diverted to carbohydrate synthesis and, therefore, plants are able to achieve net synthesis of carbohydrate from acetyl-CoA. 

Fig. 6. Electron transport in plants and fimgi. Three complexes (7, II and IV) translocate protons to gradient across the mitochondrial membrane Complex 7NADH dehydrogenase complex II succinate dehydrogenase complex III cytochrom be, complex IV cytochrome c oxidase (Cox). Cyc Cytochrome c UbiQ ubiquinone Aox alternative oxidase SHAM salicylhy-droxamic acid AA antimycin A KCN potassimn cyanide. (From Vanlerberghe and McIntosh [137])...

Malonic add HOOC-CH2-COOH, a dicarboxyl-ic acid, m.p. 135.6 °C, which has been found in the free form in plants, but is of only sporadic occurrence. At the pH of the cell M.a. is present as its anion (mal-onate), which is a known competitive inhibitor of succinate dehydrogenase in the tricarboxylic acid cycle. A metabolically important derivative of M.a. is malo-nyl-CoA, an intermediate of Fatty acid biosynthesis (see). 

Fig. 60. The respiratory chain of higher plants. Ubiquinone appears to serve as an electron reservoir. = probable site of ATP formation. SD = succinate dehydrogenase. It used to be assumed that, with the exception of the reaction catalyzed by SD, the hydrogen acceptor in dehydrogenation reactions was NAD+ and that the hydrogen then entered the respiratory chain in the form of NADH+H+. In reality the situation is more complicated since the lipoic acid oxidizing flavoproteid of the pyruvate dehydrogenase and the a-ketoglutarate dehydrogenase complexes—in both cases the same flavoproteid is involved—can establish direct contact with the flavoproteins of the respiratory chain just like succinate dehydrogenase. associated with encircled flavoproteins means that ATP can be formed as a result of transitions between the various flavoproteins, except those involving SD.

---