Cited by 165Mitochondrial Function and PathologyBiochemical Acid Research StudiesAdipose Tissue and Metabolism

Role of calcium ions in the regulation of intramitochondrial metabolism. Properties of the Ca2+-sensitive dehydrogenases within intact uncoupled mitochondria from the white and brown adipose tissue of the rat

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McCormack, J G, Denton, R M·1980·Biochemical Journal

Abstract

1. Increasing concentrations of both Ca2+ and Sr2+ (generated by using EGTA buffers) resulted in 4-fold increases in the initial activity of pyruvate dehydrogenase within intact uncoupled mitochondria from rat epididymal adipose tissue incubated in the presence of the ionophore A23187, ATP, Mg2+ and oligomycin. The k0.5 values (concentrations required for half-maximal effects) for Ca2+ and Sr2+ were 0.54 and 7.1 microM respectively. In extracts of the mitochondria, pyruvate dehydrogenase phosphate phosphatase activity was stimulated about 4-fold by Ca2+ and Sr2+, with k0.5 values of 1.08 and 6.4 microM respectively. 2. NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase appeared to be rate-limiting in the oxidation of threo-Ds-isocitrate and oxoglutarate by uncoupled mitochondria from brown adipose tissue of cold-adapted rats. Ca2+ (and Sr2+) diminished the Km for the oxidation of both threo-Ds-isocitrate and oxoglutarate. The kinetic constants for these oxidations were very similar to those obtained for the activities of NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase in extracts of the mitochondria. In particular, the k0.5 values for Ca2+ were all in the range 0.2–1.6 microM and Sr2+ was found to mimic Ca2+, but with k0.5 values about 10 times greater. 3. Overall, the results of this study demonstrate that the activities of pyruvate dehydrogenase, NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase may all be increased by Ca2+ and Sr2+ within intact mitochondria. In all cases the k0.5 values are close to 1 and 10 microM respectively, as found for the separated enzymes. Experiments on brown-adipose-tissue mitochondria incubated in the presence of albumin suggest that it may be possible to use the sensitivity of the dehydrogenases to Ca2+ as a means of assessing the distribution of Ca2+ across the mitochondrial inner membrane.

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  • Support for a role of ROS in HIF-1α stabilization derives from studies showing that the absence of cytochrome c or blocked Rieske Fe-S proteins under hypoxic conditions blocks HIF-1α stabilization.

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  1. Plaut, G. W. E. & Smith, C. M. (1977) in PIvridine Nucleotide-Depenideni DehYdrogenases (Sund. H.. ed.), pp. 444-457, Walter de Gruyter, Berlin

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Authors
McCormack, J. G., & Denton, R. M.
Affiliations
University of Bristol (GB)
Venue
Biochemical Journal
Published
1980-07-15
Volume
190
Issue
1
Pages
95-105
ISSN
0264-6021 (ISSN-L)
OpenAlex
W130501137
Cited by
165
References
17
Citations by year
2026: 2 · 2025: 4 · 2024: 5 · 2023: 3 · 2022: 4 · 2021: 6 · 2020: 2 · 2019: 2 · 2018: 5 · 2017: 3 · 2016: 1 · 2015: 2 · 2013: 4 · 2012: 3
FWCI
5.68
Type
journal article
Language
en
Open access
Locations
  • Biochemical Journal (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Mitochondrial Function and Pathology
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Biochemical Acid Research Studies
  • Health Sciences › Medicine › Physiology › Adipose Tissue and Metabolism
Keywords
calcium ions, pyruvate dehydrogenase, NAD-isocitrate dehydrogenase, 2-oxoglutarate dehydrogenase, strontium, white adipose tissue, brown adipose tissue, cold adaptation, substrate Km, A23187
MeSH terms
Calcimycin, Adenosine Triphosphate, Adipose Tissue, Animals, Adipose Tissue, Brown, Calcium, Kinetics, Male, Mitochondria, Oxidoreductases, Serum Albumin, Bovine, Strontium, Rats, In Vitro Techniques

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