What question did this study set out to answer?

To determine the observed equilibrium constants (Kobs) and free energy changes for malate dehydrogenase, citrate synthase, citrate lyase, and acetyl-CoA hydrolysis under near-physiological conditions.

October 1, 1973Journal of Biological ChemistryOpen Access

Equilibrium Constants of the Malate Dehydrogenase, Citrate Synthase, Citrate Lyase, and Acetyl Coenzyme A Hydrolysis Reactions under Physiological Conditions

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Authors

RGRobert W. GuynnNorthwestern University HGHarris J. GelbergLAC+USC Medical Center RVRichard L. VeechNational Institutes of Health

Discussion

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Implication

Biochemical investigation reveals thermodynamic equilibrium constants of key mitochondrial enzymes, indicating precise energetic profiles of cellular metabolism.

Key Points

To determine the observed equilibrium constants (Kobs) and free energy changes for malate dehydrogenase, citrate synthase, citrate lyase, and acetyl-CoA hydrolysis under near-physiological conditions.
Measured equilibrium constants in vitro at 38 °C, pH 7.0, ionic strength I = 0.25, and varying free Mg2+ concentrations (0 to 10^-3 M).
Calculated the observed standard free energy change (ΔG0obs) of acetyl-CoA hydrolysis directly from the measured citrate synthase and citrate lyase constants.
Under 1 mM free Mg2+, Kobs was (2.86 ± 0.12) × 10^-5 for malate dehydrogenase, (2.24 ± 0.11) × 10^6 for citrate synthase, and 2.22 ± 0.16 M^-1 for citrate lyase.
Malate dehydrogenase activity was unaffected by free Mg2+ up to 4 mM, whereas citrate synthase and citrate lyase shifted identically as Mg2+ decreased to 0 (yielding Kobs of (1.01 ± 0.05) × 10^6 and 1.00 ± 0.07 M^-1, respectively).
The calculated Kobs for acetyl-CoA hydrolysis was 1.01 × 10^6 M, yielding a ΔG0obs of -8.54 kcal/mol (-35.75 kJ/mol) independent of magnesium concentration.

Cite This Study

Guynn et al. (1973) studied this question.

synapsesocial.com/papers/6a845bfff6d812dcfa83de8a https://doi.org/10.1016/s0021-9258(19)43346-2

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October 1, 1973Journal of Biological ChemistryOpen Access

Equilibrium Constants of the Malate Dehydrogenase, Citrate Synthase, Citrate Lyase, and Acetyl Coenzyme A Hydrolysis Reactions under Physiological Conditions

View Full Paper

Ask AI

Bookmark

Authors

RGRobert W. GuynnNorthwestern University HGHarris J. GelbergLAC+USC Medical Center RVRichard L. VeechNational Institutes of Health

Discussion

Member takes

Implication

Biochemical investigation reveals thermodynamic equilibrium constants of key mitochondrial enzymes, indicating precise energetic profiles of cellular metabolism.

Key Points

To determine the observed equilibrium constants (Kobs) and free energy changes for malate dehydrogenase, citrate synthase, citrate lyase, and acetyl-CoA hydrolysis under near-physiological conditions.
Measured equilibrium constants in vitro at 38 °C, pH 7.0, ionic strength I = 0.25, and varying free Mg2+ concentrations (0 to 10^-3 M).
Calculated the observed standard free energy change (ΔG0obs) of acetyl-CoA hydrolysis directly from the measured citrate synthase and citrate lyase constants.
Under 1 mM free Mg2+, Kobs was (2.86 ± 0.12) × 10^-5 for malate dehydrogenase, (2.24 ± 0.11) × 10^6 for citrate synthase, and 2.22 ± 0.16 M^-1 for citrate lyase.
Malate dehydrogenase activity was unaffected by free Mg2+ up to 4 mM, whereas citrate synthase and citrate lyase shifted identically as Mg2+ decreased to 0 (yielding Kobs of (1.01 ± 0.05) × 10^6 and 1.00 ± 0.07 M^-1, respectively).
The calculated Kobs for acetyl-CoA hydrolysis was 1.01 × 10^6 M, yielding a ΔG0obs of -8.54 kcal/mol (-35.75 kJ/mol) independent of magnesium concentration.

Cite This Study

Guynn et al. (1973) studied this question.

synapsesocial.com/papers/6a845bfff6d812dcfa83de8a https://doi.org/10.1016/s0021-9258(19)43346-2

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