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2.2: Catabolism of glucose-glycolysis as the first pathway tells us about some general metabolic principles

Tables of standard free energies of hydrolysis

Table A.  Compounds considered to be "High Energy" Compounds 

Pi= inorganic phosphate (doesn’t specify a species) = major species at biological pH is \(\mathrm{HPO_{4}^{2-}}\)

Compound

(hydrolysis reaction is shown where more than one is possible)

\(\mathrm{\Delta G^{\circ'}\: (kJ/mol)}\) Transfer Potential=\(\mathrm{|\Delta G ^{\circ'}|}\) Compound type

Reason for large \(\mathrm{\Delta G^{\circ'}}\) of hydrolysis

S=Substrate

P=Product

PEP -61.9 61.9 Enolic phosphate

P tatuomerizes (pyruvate)

P resonance stability (Pi)

1,3-bisPGA -49.3 49.3 Acyl phosphate (phosphoric acid + carboxylic acid)

P ionizaiton (PGA)

Increased P resonance stability (Pi and PGA)

Phosphocreatine -43.0 43.0 Guanidine phoshpate P resonance stability
\(\mathrm{ATP \rightarrow AMP + PPi}\) -45.6 45.6 Phosphoric acid anhydride

P resonance stability

P ionization

S bond strain due to electrostatic repulsion

\(\mathrm{ADP \rightarrow AMP + Pi}\) -32.8 32.8 Phosphoric acid anhydirde Same as for \(\mathrm{ATP \rightarrow AMP + P}\)
\(\mathrm{ATP \rightarrow ADP + Pi}\) -30.5 30.5 Phosphoric acid anhydride Same as for \(\mathrm{ATP \rightarrow AMP + P}\)
UDP-Glucose -31.9 31.9 Sugar nucleotide

P resonance stability

P ionization

Acetyl Coenzyme A -31.4 31.4 Thioester

S no resonance stabilization

P ionization

P resonance stabilization

S-adenosylmethionine -25.6 25.6 Sulfonium salt

Sulfur more stable in P

P less charge repulsion

 

Table B.  Compounds considered NOT to be "High Energy" Compounds

Compound \(\mathrm{\Delta G ^{\circ'}\: (kJ/mol)}\) Transfer Potential Compound type Reason for \(\mathrm{\Delta G^{\circ'}}\) of hydrolysis smaller than compounds in Table A.
\(\mathrm{AMP \rightarrow adenosine + Pi}\) -14.2 14.2 Phosphate ester

S no destabilizing electrostatic repulsion

P (Adenine) doesn't ionize

\(\mathrm{Glc-6-P \rightarrow Glc + HPO_{4}^{2-}}\) -13.8 13.8 Phosphate ester S no electrostatic repulsion

 

"high energy" bonds are those whose hydrolysis proceeds with \(\mathrm{\Delta G ^{\circ’}}\) more negative than -25kJ/mol

Most values from Principles of Biochemistry pp. 521.

Systematic Common
ATP:hexose 6-phosphotransferase Hexokinase
ATP:GLC 6-phosphotransferase Glucokinase (liver)
GLC-6-P ketolisomerase Phosphoglucose isomerase
ATP:F-6-P 1-phosphotransferase Phosphofructokinase-1 (PFK-1)
F-1,6-bisP G-3-P-lyase aldolase
G-3-P ketolisomerase Triose phosphate isomerase
G-3-P:(\mathrm{NAD^{+}}\) oxidoreductase (phosphorylating) G-3-P dehydrogenase
ATP:3-PGA 1-phosphotransferase Phosphoglycerate kinase
3-PGA 2,3-phosphoisomerase Phosphoglycerate mutase
2-PGA hydro-lyase Enolase
ATP:enol-pyruvate phosphotransferase Pyruvate kinase
Lactate:\(\mathrm{NAD^{+}}\) oxidoreductase Lactate dehydrogenase
Pyruvate carboxy-lyase Pyruvate decarboxylase
Ethanol:\(\mathrm{NAD^{+}}\) oxidoreductase Alcohol dehydrogenase