Glycolysis only, ATP Dependent Group Transfer Reaction

Gluconeogenesis Only, Hydrolysis Reaction

Readily Reversible, Both Glycolysis and Gluconeogenesis, Isomerization Reaction

Reversible, Both Glycolysis and Gluconeogenesis, C-C bond aldol Reaction. Standard State Thermodynamics (ΔG^o') favors gluconeogenesis, but under normal physiological conditions the ΔG favors glycolysis

Both glycolysis and gluconeogenesis. Two sequential reaction types on the same enzyme active site.

NAD⁺ dependent REDOX
hydrolysis equivalent

Both glycolysis and gluconeogenesis. ATP Dependent group Transfer Reaction. Unlike the two similar ATP dependent reactions above, this reaction is readily reversible.

The Standard State thermodynamics (ΔG^o') greatly favors ATP production
The high ATP concentration relative to ADP evens this out substantially such that the ΔG is very close to zero.

Both glycolysis and gluconeogenesis. Group Transfer reaction. While the substrate and product are isomers this is NOT an isomerization reaction

Both glycolysis and gluconeogenesis. Dehydration Reaction- in the direction of glycolysis the equivalent of water is removed between C2 and C3. In the direction of gluconeogenesis water is added across the C2-C3 double bond.

Gluconeogenesis only. Two successive steps

Aldol Reaction to cleave off the CO₂
simultaneous to a "ATP" dependent Group Transfer

The release of CO²drives this reaction both in the standard state and in the current conditions

Gluconeogenesis only. Aldol reaction to add CO₂. In order to add CO₂ ATP must be expended. Check out the page to see how and why.

Anaerobic Glucose Metabolism

Glycolysis and Gluconeogenesis

Enzymes exclusive to Glycolysis

Enzymes Shared between the two pathways

Enzymes exclusive to gluconeogenesis

Get a "quick summary" by hovering over a link. Follow the links on the enzyme name to learn more about its chemistry and its catalytic mechanism. There are also some rationales about how the two pathways fit together, which reactions are the same and which must be different to maintain favorable standard free energies for both overall pathways.
Glycolysis Pathway			Gluconeogenesis Pathway
		Glucose
	ATP → Hexokinase ADP ←	↓ ↑	→ PO₄⁼ Glucose-6-Phosphatase
		Glucose-6-Phosphate
Phosphoglucose Isomerase
		Fructose-6-Phosphate
ATP → Phosphofructokinase ADP ←		↓ ↑	→ PO₄⁼ Fructose-1,6-Bisphosphatase
		Fructose-1,6-Bisphosphate
Fructose 1,6 Bisphosphate Aldolase
Triose Phosphate Isomerase		DiHydroxyAcetone Phosphate AND Glyceraldehyde-3-Phosphate
NAD⁺ + PO₄⁼ → Glyceraldehyde-3-Phosphate Dehydrogenase NADH ←
		1,3BisphosphoGlycerate
ADP → Phosphoglycerate Kinase ATP ←
		3-PhosphoGlycerate
Phosphoglycerate Mutase
		2-PhosphoGlycerate
enolase
		PhosphoEnolPyruvate
				→ CO₂ + GDP (ADP equivalent) PEP carboxykinase ← GTP (ATP equivalent)
Compare the glycolysis, uncatalyzed and gluconeogenesis reactions side by side	ADP → Pyruvate Kinase ATP ←	↓	oxaloacetate 4 Carbon compound
				→ADP + PO₄⁼ pyruvate carboxylase ← CO₂ + ATP
		Pyruvate
glycolysis "officially" ends here, but 1 of the 3 steps below are required!
pyruvate decarboxylase Yeasts Ethanol fermentation: Beers, Wines The CO₂ released is used to raise bread				lactate dehydrogenase Lactate fermentation:(overworked muscle cells, red blood cells, yogurt making (Lactobacillus acidophilus))
	Ethanol	↓	Lactate
	Pyruvate dehydrogenase	Acetyl-CoA
Acetyl-CoA is NOT an end point of fermentative processes like ethanol or lactate. This takes place in mitochondria and can lead to oxidative glucose metabolism. (the subject of module 7). It is a compound that can be used in many processes including synthesis of some amino acids and synthesis of all fatty acids.

Notes:

The process of glycolysis and glyconeogenesis share several reactions in common
- Most enzymes are highlighted in yellow. These are utilized for BOTH glycolysis and gluconeogenesis. Enzymes highlighted in cyan are exclusively utilized for glycolysis because of favorable ΔG^o' and/or ΔG. Those enzymes highlighted in "green" are utilized exclusively for gluconeogenesis.
- The reactions that are shared are denoted with the symbol. As these reaction proceed in EITHER direction (depending on the ΔG... more on this in two pages)
- Only one enzyme is listed for these steps since the SAME enzyme is shared in BOTH diretions
Some reactions, however, have a LARGE ΔG^o' and/or ΔG value. These reactions are denoted with
In These cases the pathways do NOT share this enzyme, and one is listed for each pathway.

In places where the arrows are not vertical... this simply denotes where one pathway uses two reactions while the other pathway utilizes only a single reaction.