Role of Glutamate-oxaloacetate Transaminase and Malate Dehydrogenase in the Regeneration of NAD for Glycine Oxidation by Spinach leaf Mitochondria.

During glycine oxidation by spinach leaf mitochondria, oxygen consumption showed a strong and transient inhibition upon addition of oxaloacetate or aspartate plus alpha-ketoglutarate. During the course of the inhibition, aspartate and alpha-ketoglutarate were stoichiometrically transformed into malate and glutamate.It is concluded that oxaloacetate formed by transamination is reduced by the malate dehydrogenase, which allows the regeneration of NAD(+) for glycine oxidation and, thus, by-passes the respiratory chain. Efficiency of a malate-glutamate/aspartate-alpha-ketoglutarate shuttle upon illumination and under in vivo conditions is discussed.