Influence of mitochondrial @entity908 kinase on the mitochondrial/extramitochondrial distribution of high energy phosphates in muscle tissue: evidence for a leak in the XXXX shuttle.

@entity35 @entity908 @entity1734 @entity10941
The influence of mitochondrial @entity908 kinase on subcellular high energy systems has been investigated using isolated @entity35 heart mitochondria, mitoplasts and intact heart and skeletal muscle tissue. In isolated mitochondria, the @entity908 kinase is functionally coupled to oxidative phosphorylation at active respiratory chain, so that it catalyses the formation of @entity1734 against its thermodynamic equilibrium. Therefore the mass action ratio is shifted from the equilibrium ratio to lower values. At inhibited respiration, it is close to the equilibrium value, irrespective of the mechanism of the inhibition. The same results were obtained for mitoplasts under conditions where the mitochondrial @entity908 kinase is still associated with the inner membrane. In intact tissue increasing amounts of @entity1734 are found in the mitochondrial compartment when respiration and/or muscle work are increased. It is suggested that at high rates of oxidative phosphorylation @entity1734 is accumulated in the intermembrane space due to the high activity of mitochondrial @entity908 kinase and the restricted permeability of reactants into the extramitochondrial space. A certain amount of this @entity1734 'leaks' into the mitochondrial matrix. This leak is confirmed in isolated @entity35 heart mitochondria where @entity1734 is taken up when it is generated by the mitochondrial @entity908 kinase reaction. At inhibited @entity908 kinase, external @entity1734 is not taken up. Likewise, mitoplasts only take up @entity1734 when @entity908 kinase is still associated with the inner membrane. Both findings indicate that uptake is dependent on the functional active @entity908 kinase coupled to oxidative phosphorylation. @entity1734 uptake into mitochondria is inhibited with @entity10941 .(ABSTRACT TRUNCATED AT 250 WORDS)
