Simonin 2012 Biochem J
|Simonin V, Galina A (2012) Nitric oxide inhibits succinate dehydrogenase-driven oxygen consumption in potato tuber mitochondria in an oxygen tension-independent manner. Biochem J 449:263-73.|
Abstract: Nitric oxide (NO) is described as an inhibitor of plant and mammalian respiratory chains due to its high affinity for cytochrome c oxidase (COX), which hinders reduction of oxygen to water. Here we show that in plant mitochondria NO may interfere with other respiratory complexes as well. We analyzed oxygen consumption supported by complex I and/or complex II and/or external NADH dehydrogenase in Percoll-isolated potato tuber (Solanum tuberosum) mitochondria. When mitochondrial respiration was stimulated by succinate, adding the NO-donors SNAP or DETA-NONOate caused a 70 % reduction in oxygen consumption rate in state 3 (stimulated with 1 mM of ADP). This inhibition was followed by a significant increase in the KM of succinate dehydrogenase (SDH) for succinate (KM of 0.77 ± 0.19 to 34.3 ± 5.9 mM, in presence of NO). When mitochondrial respiration was stimulated by external NADH dehydrogenase or complex I, NO had no effect on respiration. NO itself and DETA-NONOate had similar effects to SNAP. No significant inhibition of respiration was observed in the absence of ADP. More importantly, SNAP inhibited PTM respiration independently of oxygen tensions, indicating a different kinetic mechanism from that observed in mammalian mitochondria. We also observed, in an FAD reduction assay, that SNAP blocked the intrinsic SDH electron flow in much the same way as thenoyltrifluoroacetone (TTFA), a noncompetitive SDH inhibitor. We suggest that NO inhibits SDH in its ubiquinone site or its Fe-S centers. These data indicate that SDH has an alternative site of NO action in plant mitochondria.
• Keywords: Plant mitochondria Solanum tuberosum, Nitric oxide
• O2k-Network Lab: BR Rio de Janeiro Galina A
Labels: MiParea: Respiration
Preparation: Isolated mitochondria Enzyme: Complex I, Complex II;succinate dehydrogenase, Complex IV;cytochrome c oxidase
Coupling state: OXPHOS Pathway: N, S, NS HRR: Oxygraph-2k