Polarographic measurement of oxygen uptake by pea-root mitochondria

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Abstract
A simple polarograph and a cell containing platinum and silver/silver chloride electrodes suitable for measurement of O2 uptake are described. [alpha]-Oxoglutarate, L-malate and pyruvate were either only very slowly oxidized or not oxidized at all by pea-root mitochondria. If the mitochondria were first shaken in a water bath at 25[degree] for 1/2 hour, they then oxidized these substrates. Succinate was oxidized by the mitochondria, but the rate was increased by shaking. Stimulation of the oxidations by unshaken mitochondria was not obtained by addition of several cofactors (diphosphopyridine nucleotide, adenosine di- and tri-phosphates, thiamine pyrophosphate and coenzyme A) but the oxidations by shaken mitochondria were greatly enhanced. Cytochrome c increased the rate of oxidation of succinate and [alpha]-oxoglutarate, but could be replaced by bovine-plasma albumin. It is suggested that the action of the shaking is to make the mitochondrial membrane more permeable or to disrupt it and release the enzymes.