Further studies on the effect of phosphoenolpyruvate on respiration-dependent calcium transport by rat heart mitochondria

Abstract

Phosphoenolpyruvate was found to depress extra oxygen consumption associated with Ca 2+ -induced respiratory jump by rat heart mitochondria. Addition of phosphoenolpyruvate to mitochondria which have accumulated Ca 2+ in the presence of glutamate and inorganic phosphate causes the release of Ca 2+ from mitochondria. The phosphoenolpyruvate-stimulated Ca 2+ efflux can be observed with mitochondria loaded with low initial Ca 2+ concentration (0.12 mM) in the incubation medium. Measurements of mitochondrial H + translocation produced by addition of Ca 2+ to respiring mitochondria show that phosphoenolpyruvate depresses H + ejection and enhances H + uptake by mitochondria. The Ca 2+ -releasing effect of phosphoenolpyruvate was found to be significantly stronger than that produced by rotenone when added to mitochondria loaded with Ca 2+ in the presence of glutamate and inorganic phosphate. Dithiothreitol cannot overcome the effect of phosphoenolpyruvate on mitochondrial Ca 2+ transport. © 1976.