Open AccessPyruvate Metabolism in Mitochondria from Rat Liver
Author(s) -
Stucki Jörg W.,
Walter Paul
Publication year - 1972
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1972.tb02072.x
Subject(s) - citric acid cycle , mitochondrion , malate dehydrogenase , biochemistry , citrate synthase , metabolite , atpase , metabolism , citric acid , chemistry , energy metabolism , enzyme , biophysics , biology , endocrinology
Rat liver mitochondria were incubated in the presence of [2‐ 14 C]pyruvate, HCO 3 − , ATP and phosphate. From the measured amounts and the specific radioactivities of the products formed, metabolic fluxes through individual enzymatic reactions of pyruvate metabolism including the citric acid cycle were calculated. These fluxes and the formation of the products were simulated with a computer‐model which involved 51 reactions and 39 metabolites. Computer‐simulations and calculations of the experimental results revealed the existence of energy‐dissipating processes. About one third of the energy‐dissipation was inhibited by atractylate. It is concluded that this atractylate‐sensitive energy dissipation was due to some extramitochondrial ATPase and to the maintenance of an asymmetric distribution of ATP and ADP across the inner membrane. The atractylate‐insensitive part of energy dissipation is probably related to state 4 respiration of isolated mitochondria. Based on the specific radioactivities of malate and citrate it was concluded that the pools of malate and oxaloacetate within the matrix cannot be fully equilibrated. It is proposed that the transport of malate out of the mitochondria restricts the passage of this metabolite through the citric acid cycle.