Dynamic compartmentation of adenine nucleotides in the mitochondrial intermembrane space of rat-heart mitochondria

ADP delivery from adenylate kinase in the mitochondrial intermembrane space to oxidative phosphorylation increases in the presence of macromolecules

“…The competition between intramitochondrial and extramitochondrial ADP phosphorylation was strongly influenced by the localization of the ADP generating enzymes. PK completely suppressed the kinase-induced respiration when the ADP was formed by external yeast HK both in the absence [10,17] and in the presence (this study) of macromolecules. ADP measurements showed that the dependence of oxidative phosphorylation on bulk ADP levels was clearly different in the Mi-AK system compared to the HK system.…”

“…The ADP concentration gradient across the outer mitochondrial membrane was calculated basically as described in [10,17]. The ADP production flux by Mi-AK (VAK) was calculated from the decrease in AMP concentration, assuming that the rate was stationary throughout the 2.5 min period.…”

“…Earlier studies [10,17,21,22] in the absence of macromolecules had shown that a significant part of ADP generated by intermembrane space kinases was not accessible to extramitochondrial ADP consumers. This phenomenon can partially be explained by action of the outer membrane as a diffusion barrier for nucleotides [10,22].…”

The control of brain mitochondrial energization by cytosolic calcium: The mitochondrial gas pedal

“…The MOM acts as a remarkable diffusion barrier forming rate dependent diffusion gradients up to 12 lM ADP at maximum diffusion rates (10)(11)(12)(13). Within intact cells such diffusion gradients can probably be larger than those measured in isolated mitochondria without the oncotic pressure on the organelles.…”

Kinetic limitations in the overall reaction of mitochondrial oxidative phosphorylation accounting for flux‐dependent changes in the apparent ΔGexP/ΔH+ ratio

“…Changes in the medium are given in the legends of the figures. For determination of extramitochondrial adenine nucleotides and G-6-P, I ml samples were withdrawn from the incubation mixture and quickly filtered through glass fibre filters (Millipore Type AP 25) for separation of the mitochondria into 4 ml of a phenol/chloroform/isoamyl alcohol mixture (38:24:1) (v/v) saturated with water plus 0.6 ml of 66 mM EDTA for quenching and extraction [2]. Extramitochondrial phosphorylation potentials were calculated using a computer program [3] taking into account the standard phosphorylation potentials published in [4].…”