Novel insights in the regulation of the plant succinate dehydrogenase

Affourtit, Charles, Krab, Klaas, Leach, Graeme R, Whitehouse, David G and Moore, Anthony L (2000) Novel insights in the regulation of the plant succinate dehydrogenase. p. 126.

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We have investigated the regulation of succinate dehydrogenase (SDH) in potato tuber mitochondria by simultaneous measurement of the oxygen uptake rate and the ubiquinone-redox poise. SDH activity is stimulated by both ATP and ADP in a manner insensitive to carboxyatractyloside suggesting that activation occurs at the cytoplasmic side of the mitochondrial inner-membrane. It was found that ATP affects the SDH kinetics with respect to the Q-redox poise such that activity is considerably increased at any reduction level of the Q-pool. Using the Q-redox poise as a quantitative measure of activation, half-maximal activation by ATP was shown to occur at 2.7 µM. Interestingly, our experimental approach reveals that SDH is also activated by oligomycin (half-maximally at 16 nM). This oligomycin-induced activation results in increased SDH activities at any Q-redox poise, though the extent of stimulation is less than that caused by ATP. A comparable degree of activation was also observed when oligomycin was substituted with N,N'-dicyclohexycarbodiimide. De-energisation of the mitochondrial inner-membrane by an uncoupler results in a reversal of the oligomycin-mediated activation. Furthermore, the rate of activation by adenine nucleotides is decreased dramatically when mitochondria are pre-incubated in the presence of an uncoupler. These data indicate that, in vitro, SDH activity is regulated by the energy status of the mitochondrial inner-membrane. The possible physiological relevance of this regulatory mechanism will be discussed

Item Type: Article
Schools and Departments: School of Life Sciences > Biochemistry
Depositing User: David Whitehouse
Date Deposited: 06 Feb 2012 21:11
Last Modified: 22 May 2013 09:29
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