The mitochondrial outer membrane is not a major diffusion barrier for ADP in mouse heart skinned fibre bundles.
The response of mitochondrial oxygen consumption to ADP in saponin-skinned cardiac fibre bundles has an apparent Km an order of magnitude higher than that in isolated mitochondria. Here we report that incubating skinned cardiac fibre bundles from wild-type mice or double-knockout mice lacking both cytosolic and mitochondrial creatine kinase (CK) with CK and creatine or with yeast hexokinase and glucose as extramitochondrial ADP-producing systems decreases the apparent Km of the bundles for ADP severalfold. We conclude that the affinity of mitochondria for ADP in mouse heart is of the same order of magnitude as that of isolated mitochondria, while the high apparent Km of the bundles is caused by diffusion gradients outside the mitochondria.
Kongas
Olav
O
Department of Mechanics and Applied Mathematics, Institute of Cybernetics, Tallinn Technical University, Akadeemia 21, 12618 Tallinn, Estonia. kongas@ioc.ee
Wagner
Marijke J
MJ
ter Veld
Frank
F
Nicolay
Klaas
K
van Beek
Johannes H G M
JH
Krab
Klaas
K
D000244:Adenosine Diphosphate / Q000502:physiology*; D000818:Animals; D003402:Creatine Kinase / Q000172:deficiency / Q000235:genetics; D052281:Creatine Kinase, Mitochondrial Form; D004058:Diffusion; D004305:Dose-Response Relationship, Drug; D007425:Intracellular Membranes / Q000201:enzymology / Q000378:metabolism / Q000502:physiology*; D007527:Isoenzymes / Q000172:deficiency / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D008929:Mitochondria, Heart / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*
D007527:Isoenzymes; D000244:Adenosine Diphosphate; D003402:Creatine Kinase; D052281:Creatine Kinase, Mitochondrial Form