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Am J Physiol Cell Physiol (May 1, 2002). doi:10.1152/ajpcell.00101.2002
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Articles in PresS, published online ahead of print May 1, 2002
Am J Physiol Cell Physiol, 10.1152/ajpcell.00101.2002
Submitted on March 6, 2002
Accepted on April 29, 2002

High Km of oxidative phosphorylation for ADP in skinned muscle fibers: Where does it stem from?

Olav Kongas1*, Tai L. Yuen2, Marijke J. Wagner2, Johannes H.G.M. van Beek2, and Klaas Krab2

1 Institute for Cardiovascular Research, Vrije Universiteit Medical Center, Amsterdam, The Netherlands; Department of Mechanics and Applied Mathematics, Tallinn Technical University, Institute of Cybernetics, Tallinn, Estonia
2 Department of Molecular Cell Physiology, Vrije Universiteit, Faculty of Earth and Life Sciences, Amsterdam, The Netherlands

* To whom correspondence should be addressed. E-mail: kongas{at}ioc.ee.

Mitochondria in saponin-skinned cardiac fiber bundles were reported to have an order of magnitude lower apparent affinity to ADP than isolated mitochondria. Although ADP was measured outside the bundles, it was thought that the low affinity was not caused by diffusion gradients because of relatively short diffusion distances. Here we test the hypothesis that considerable ADP diffusion gradients exist and can be diminished by increasing the intrafiber ADP production rate. We increased the ADP producing activity in rat heart skinned fiber bundles by incubating with 100 IU/ml yeast hexokinase and glucose. Consequently, we observed a significant decrease of apparent Km to ADP of the respiration rate of bundles from 216 ± 59 to 50 ± 9 µM. Fitting the results with a mathematical model, we estimated the Km of mitochondria in the bundles to be 25 µM. We conclude that the affinity to ADP of in situ mitochondria in heart is of the same order of magnitude as that of isolated mitochondria.




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J. H. G. M. van Beek
Adenine nucleotide-creatine-phosphate module in myocardial metabolic system explains fast phase of dynamic regulation of oxidative phosphorylation
Am J Physiol Cell Physiol, September 1, 2007; 293(3): C815 - C829.
[Abstract] [Full Text] [PDF]


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