Table 2.

The reaction and K _eq of high‐activity enzymes used to calculate the ratios of the free coenzyme couples

Enzymes	Reactions	K eq	References
High‐activity cytoplasmic NAD‐linked dehydrogenases
Lactate dehydrogenase EC 1.1.1.27	$\frac{\left[{\text{pyruvate}}^{‐1}\right]\left[\text{NADH}\right]\left[{\mathrm{H}}^{+}\right]}{\left[{\text{lactate}}^{‐1}\right]\left[{\mathrm{NAD}}^{+}\right]}$	=1.11   × 10−11 M	7
Malate dehydrogenase NAD (cytoplasmic) EC 1.1.1.37	$\frac{\left[{\text{oxaloacetate}}^{2‐}\right]\left[\text{NADH}\right]\left[{\mathrm{H}}^{+}\right]}{\left[{\text{malate}}^{2‐}\right]\left[{\mathrm{NAD}}^{+}\right]}$	=2.86 × 10−12 M	24
Glycerol‐3‐phosphate dehydrogenase EC 1.1.1.8	$\frac{\left[{\text{DHAP}}^{2‐}\right]\left[\text{NADH}\right]\left[{\mathrm{H}}^{+}\right]}{\left[\text{glycerol}3‐{\text{phosphate}}^{2‐}\right]\left[{\mathrm{NAD}}^{+}\right]}$	=1.35 × 10−11 M	25
Glyceraldehyde 3P dehydrogenase EC 1.2.1.12	$\frac{\left[\mathrm{D}‐\text{glycerate}1,3‐{\text{bisphosphate}}^{4‐}\right]\left[\text{NADH}\right]\left[{\mathrm{H}}^{+}\right]}{\left[\text{glyceraldehyde}3{\mathrm{P}}^{2‐}\right]\left[{\mathrm{NAD}}^{+}\right]\left[{\mathrm{HPO}}_4^{2-}\right]}$	=0.51 × 10−7M	26
High‐activity mitochondrial NAD‐linked dehydrogenases
β‐Hydroxybutyrate dehydrogenase EC 1.1.1.30	$\frac{\left[{\text{acetoacetate}}^{‐1}\right]\left[\text{NADH}\right]\left[{\mathrm{H}}^{+}\right]}{\left[\beta ‐{\text{hydroxybutyrate}}^{‐1}\right]\left[{\mathrm{NAD}}^{+}\right]}$	= 4.93 × 10−9 M	7
Glutamate Dehydrogenase EC 1.4.1.2	$\frac{\left[\alpha ‐{\text{ketoglutarate}}^{2‐}\right]\left[{\mathrm{NH}}_4^{+}\right]\left[\text{NADH}\right]\left[{\mathrm{H}}^{+}\right]}{\left[{\text{glutamate}}^{2‐}\right]\left[{\mathrm{NAD}}^{+}\right]}$	=3.87 ×10−13 M2	27
High‐activity cytoplasmic NADP‐linked dehydrogenases
Isocitrate dehydrogenase EC 1.1.1.41	$\frac{\left[\alpha ‐{\text{ketoglutarate}}^{2‐}\right]\left[\text{NADPH}\right]\left[{\mathrm{CO}}_2\right]}{\left[{\text{isocitrate}}^{3‐}\right]\left[{\text{NADP}}^{+}\right]}$	=1.17 M	28
Glutathione reductase EC 1.6.4.2	$\frac{\left[\text{GSSG}\right]\left[\text{NADPH}\right]\left[{\mathrm{H}}^{+}\right]}{{\left[\mathrm{GSH}\right]}^2\left[{\text{NADP}}^{+}\right]}$	=100 × 10−7	29
6‐P Gluconate dehydrogenase EC 1.1.1.44	$\frac{\left[\text{ribulose}5{\mathrm{P}}^{2‐}\right]\left[\text{NADPH}\right]\left[{\mathrm{CO}}_2\right]}{\left[6\mathrm{P}{\text{gluconate}}^{3‐}\right]\left[{\text{NADP}}^{+}\right]}$	=1.72 × 10−1 M	30
Malic enzyme EC 1.1.1.39	$\frac{\left[{\text{pyruvate}}^{‐}\right]\left[\text{NADPH}\right]\left[{\mathrm{CO}}_2\right]}{\left[{\text{malate}}^{3‐}\right]\left[{\text{NADP}}^{+}\right]}$	=3.44 × 10−2 M	31
High‐activity kinases at 1 mM free [Mg 2+ ]
Creatine phosphokinase EC 2.7.3.2	$\frac{\left[{\mathrm{ATP}}^{4‐}\right]\left[\text{creatine}\right]}{\left[{\mathrm{ADP}}^{3‐}\right]\left[\text{creatine}‐{\mathrm{P}}^{2‐}\right]\left[{\mathrm{H}}^{+}\right]}$	=1.66 × 10−9 M−1	32
Phosphoglycerate kinase EC 2.7.2.3	$\frac{\left[1,3\mathrm{diP}{\text{glycerate}}^{4‐}\right]\left[{\mathrm{ADP}}^{3‐}\right]}{\left[3‐\mathrm{P}{\text{glycerate}}^{3‐}\right]\left[{\mathrm{ATP}}^{4‐}\right]}$	=3,600	26
Combined KGAPDH + K3PGK	$\frac{\left[3{\mathrm{PG}}^{3‐}\right]\left[{\mathrm{ATP}}^{4-}\right]\left[\text{NADH}\right]\left[{\mathrm{H}}^{+}\right]}{\left[{\mathrm{GAP}}^{2‐}\right]\left[{\mathrm{ADP}}^{3‐}\right]\left[{\mathrm{NAD}}^{+}\right]\left[{\mathrm{HPO}}_4^{2‐}\right]}$	=1830 × 10−10	26
Adenylate kinase EC 2.7.4.3	$\frac{{\left[{\mathrm{ADP}}^{3‐}\right]}^2}{\left[{\mathrm{ATP}}^{4‐}\right]\left[{\mathrm{AMP}}^{2‐}\right]}$	=1.05	32
Acetyl CoA enzymes cytoplasm
Citrate cleavage enzyme cytoplasm EC 4.1.3.8	$\frac{\left[\text{acetylCoA}\right]\left[\mathrm{AD}{\mathrm{P}}^{3-}\right]\left[\mathrm{HP}{\mathrm{O}}_4^{2-}\right]\left[\text{oxaloacetat}{\mathrm{e}}^{2-}\right]}{\left[\mathrm{CoA}\right]\left[\mathrm{AT}{\mathrm{P}}^{4-}\right]\left[\text{citrat}{\mathrm{e}}^{3-}\right]}$	=0.985 M	33
Acetyl CoA enzymes mitochondria
Citrate synthase EC 2.3.3.1	$\frac{\left[\mathrm{CoA}\right]\left[{\mathrm{H}}^{+}\right]\left[{\text{citrate}}^{3-}\right]}{\left[\text{acetylCoA}\right]\left[{\mathrm{H}}_2\mathrm{O}\right]\left[{\text{oxaloacetate}}^{2-}\right]}$	=2.24 × 106	24
Isomerases
Triose phosphate isomerase EC 5.3.1.1	$\frac{\left[{\text{DHAP}}^{2‐}\right]}{\left[{\mathrm{GAP}}^{2-}\right]}$	=22	34
Aldolase EC 4.1.2.13	$\frac{\left[{\text{DHAP}}^{2‐}\right]\left[{\mathrm{GAP}}^{2-}\right]}{\left[{\mathrm{FDP}}^{4‐}\right]}$	=0.99 × 10−4 M	34
Transaminases
Aspartate amino transferase EC 2.6.1.1	$\frac{\left[{\text{oxaloacetate}}^{2‐}\right]\left[{\text{glutamate}}^{-}\right]}{\left[\alpha ‐{\text{ketoglutarate}}^{2‐}\right]\left[{\text{aspartate}}^{‐}\right]}$	=6.61	8
Alanine amino transferase EC 2.6.1.2	$\frac{\left[{\text{pyruvate}}^{‐}\right]\left[{\text{glutamate}}^{-}\right]}{\left[\text{alanine}\right]\left[\alpha ‐{\text{ketoglutarate}}^{2‐}\right]}$	=1.52	8

The concentrations of substrates and products and the K _eq of these reactions plug into the mass action equation allowing one to solve for the coenzyme couples: [NAD+]/[NADH], [NADP+]/[NADPH], [acetyl CoA]/[CoA] and [ATP]/[ADP]x[Pi]. The K _eq constants all assume a pH of zero, a convention used in calculating K _eq, which must be adjusted to account for physiological pH. Abbreviations: DHAP: dihydroxyacetone phosphate; FDP: fructose 1,6‐diphosphate; GAP: glyceraldehyde 3‐phosphate; GAPDH: glyceraldehyde 3‐phosphate dehydrogenase; 3PG: 3‐ phosphoglycerate; 3PGK: 3‐ phosphoglycerate kinase.