Proton re-uptake partitioning between uncoupling protein and ATP synthase during benzohydroxamic acid-resistant state 3 respiration in tomato fruit mitochondria.
The yield of oxidative phosphorylation in isolated tomato fruit mitochondria depleted of free fatty acids remains constant when respiratory rates are decreased by a factor of 3 by the addition of n-butyl malonate. This constancy makes the determination of the contribution of the linoleic acid-induced energy-dissipating pathway by the ADP/O method possible. No decrease in membrane potential is observed in state 3 respiration with increasing concentration of n-butyl malonate, indicating that the rate of ATP synthesis is steeply dependent on membrane potential. Linoleic acid decreases the yield of oxidative phosphorylation in a concentration-dependent manner by a pure protonophoric process like that in the presence of FCCP. ADP/O measurements allow calculation of the part of respiration leading to ATP synthesis and the part of respiration sustained by the dissipative H(+) re-uptake induced by linoleic acid. Respiration sustained by this energy-dissipating process remains constant at a given LA concentration until more than 50% inhibition of state 3 respiration by n-butyl malonate is achieved. The energy dissipative contribution to oxygen consumption is proposed to be equal to the protonophoric activity of plant uncoupling protein divided by the intrinsic H(+)/O of the cytochrome pathway. It increases with linoleic acid concentration, taking place at the expense of ADP phosphorylation without an increase in the respiration.
Jarmuszkiewicz
W
W
Departamento de Patologia Clinica, Faculdade de Ciências Médicas, Universidade Estadual de Campinas, 13083-970 Campinas SP, Brazil.
Almeida
A M
AM
Vercesi
A E
AE
Sluse
F E
FE
Sluse-Goffart
C M
CM
D006877:Hydroxamic Acids / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000378:metabolism / Q000648:ultrastructure; D008928:Mitochondria / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D017494:Proton Pumps / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D011522:Protons
D006877:Hydroxamic Acids; D017494:Proton Pumps; D011522:Protons; D006180:Proton-Translocating ATPases; C006696:benzohydroxamic acid