Cited by 79Mitochondrial Function and PathologyBiochemical Acid Research StudiesBiochemical and Molecular Research

Activity of purified NAD-specific isocitrate dehydrogenase at modulator and substrate concentrations approximating conditions in mitochondria

Gabriel, Jerome L., Zervos, Paula R., Plaut, Gerhard W.E.·1986·Metabolism

Abstract

The kinetic parameters of NAD-specific isocitrate dehydrogenase from bovine heart were examined at levels of substrates and effectors approximating the concentrations reported for isolated intact heart mitochondria in different respiratory states. The effect of changing ADP/ATP ratios (with total adenine nucleotides constant at 8 mmol/L) on enzyme activity was measured at constant concentrations of the substrates magnesium D-isocitrate (0.10 mmol/L) and NAD+ (3.0 mmol/L), the positive effector magnesium citrate (1.0 mmol/L) and the negative effector NADPH (1.5 mmol/L) at pH 7.4. Enzyme activity increased with increasing ADP/ATP ratios as a result of activation by rising ADP concentrations and not due to decreasing inhibition by falling levels of ATP. Increasing ADP decreased the inhibition by NADPH, and this effect was enhanced by magnesium citrate and by free Ca2+. In incubation media containing all of the above effectors, the S0.5 for enhancement of activity by free Ca2+ was 10 to 20 mumol/L at ratios of total ADP/total ATP between 2.0 and 0.1. This value is in the range of intramitochondrial concentrations of free Ca2+,1 but it is appreciably larger than S0.5 of Ca2+ (0.6 to 1 mumol/L) for the enhancement of ADP activation, which was determined in the absence of other effectors. When both the NAD+/NADH and the ADP/ATP ratios were decreased, a further decline in activity was found. The effect of the decreasing NAD+/NADH ratio was due to inhibition by NADH (apparent I0.5 = 0.23 +/- 0.03 mmol/L) since NAD+ was saturating over the range examined.

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Crossref · 10.1016/0026-0495(86)90175-7

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  • High ATP/ADP ratios allosterically inhibit IDH, decelerating the cycle upon excess energy supply.

    “OXPHOS activity also signals to the TCA cycle at the level of ATP: high ATP/ADP ratios allosterically inhibit IDH, resulting in a deceleration of the cycle upon excess energy supply (135).”

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Authors
Gabriel, J. L., Zervos, P. R., & Plaut, G. W. E.
Affiliations
Temple University (US)
Venue
Metabolism
Publisher
Elsevier BV
Published
1986-07
Volume
35
Issue
7
Pages
661-667
ISSN
0026-0495 (ISSN-L)
OpenAlex
W1996736495
Cited by
79
References
36
Citations by year
2026: 1 · 2025: 5 · 2024: 4 · 2023: 5 · 2022: 5 · 2021: 7 · 2020: 5 · 2019: 2 · 2018: 3 · 2017: 3 · 2016: 3 · 2015: 1 · 2014: 2 · 2013: 6 · 2012: 2
FWCI
0.58
Type
journal article
Language
en
Open access
closed
Locations
  • Metabolism (publishedVersion)
  • PubMed (publishedVersion)
Funders
National Institutes of Health (AM 15404)
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
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Biochemical and Molecular Research
Keywords
enzyme kinetics, ATP/ADP ratio, NAD+/NADH ratio, NADPH inhibition, magnesium citrate, free calcium, heart mitochondria, substrate inhibition, enzyme activation, bovine heart
MeSH terms
Adenosine Diphosphate, Adenosine Triphosphate, Animals, Cattle, Isocitrate Dehydrogenase, Kinetics, Mitochondria, Heart, NAD, In Vitro Techniques

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