Distribution of flux control among the enzymes of mitochondrial oxidative phosphorylation in calcium-activated saponin-skinned rat musculus soleus fibers.
Metabolic control analysis was applied to describe the control of mitochondrial oxidative phosphorylation in calcium (approximately 2 microM free calcium) activated saponin-skinned rat musculus soleus fibers oxidizing glutamate and malate. Under these circumstances approximately 80% of mitochondrial active-state respiration was reached due to the activation of ATP turnover by actomyosin ATPase. The flux control coefficients of H(+)-ATPase, adenine-nucleotide translocase, phosphate transporter, NADH:ubiquinone oxidoreductase and cytochrome-c oxidase were determined to be equal to 0.16 +/- 0.08 (n = 6), 0.34 +/- 0.12 (n = 5), 0.08 +/- 0.03 (n = 5), 0.01 +/- 0.006 (n = 4) and 0.09 +/- 0.03 (n = 3) using inhibitor titrations with the specific inhibitors oligomycin, carboxyatractyloside, mersalyl, rotenone and cyanide, respectively, and applying non-linear regression of the entire titration curve. The flux control coefficient of actomyosin ATPase was determined with vanadate to be equal to 0.50 +/- 0.09 (n = 6), measuring independently the vanadate-caused inhibition of fiber respiration and ATP-splitting activity. In contrast to results with isolated rat skeletal muscle mitochondria reconstituted with soluble F1-ATPase the decrease in phosphate concentration from 10 mM to 1 mM only slightly affected the distribution of flux control coefficients. This difference is caused by different kinetic properties of soluble F1-ATPase and actomyosin ATPase. Therefore, phosphate seems to be in skeletal muscle in vivo only a modest modulator of control of oxidative phosphorylation.
Wisniewski
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Neurobiochemisches Labor der Klinik für Neurologie and Institut für Biochemie, Otto-von-Guericke-Universität Magdeburg, Germany.
Gellerich
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FN
Kunz
W S
WS
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004789:Enzyme Activation; D066298:In Vitro Techniques; D008297:Male; D008931:Mitochondria, Muscle / Q000201:enzymology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D010085:Oxidative Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D012503:Saponins / Q000494:pharmacology
D012503:Saponins; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D002118:Calcium