Notable Steps in Glycolysis
HOCH2
O
PiOCH2
glucose
ATP
OH
PFK-1
phosphofructokinase-1
3
ADP
ADP
PiOCH2
O
glucose-6-phosphate
PiOCH2
OH
OH
HO
Not an equilibrium reaction. Not reversible.
O
HO
OH
Not an equilibrium reaction. Not reversible.
OPi
O
C
O
C
OH
phosphoenolpyruvate
C
CH2OPi
H2C
ADP
OPi
ADP
phosphoglycerate kinase
7
CH2OPi
OH
C
H
O
fructose-1,6-bisphosphate
OH
glycerate-1,3-bisphosphate
OH
OH
ATP
hexokinase
CH2OH
HO
OH
HO
1
O
fructose-6-phosphate
OH
pyruvate kinase
10
ATP
ATP
O
O
O
C
O
C
pyruvate
glycerate-3-phosphate
H
C
OH
C
H3C
O
CH2OPi
Equilibrium reaction. Reversible.
Not an equilibrium reaction. Not reversible.
Regulation of Glycolysis occurs at "irreversible" reactions
Enzyme/Reaction
Hexokinase (1)
(1)
(3)
glucose
glucose-6-Pi
Phosphofructokinase-1
fructose-6-Pi
bisPi
fructose-1,6-
Pyruvate kinase
(10) phosphoenol pyruvate
pyruvate
activator
inhibitor
glucose-6-phosphate
ATP
Regulation of Glycolysis occurs at "irreversible" reactions
Enzyme/Reaction
Hexokinase (1)
(1)
(3)
glucose
glucose-6-Pi
Phosphofructokinase-1
fructose-6-Pi
bisPi
fructose-1,6-
Pyruvate kinase
(10) phosphoenol pyruvate
pyruvate
activator
inhibitor
glucose-6-phosphate
ATP
fructose-2,6-bisphosphate Citrate
AMP
ATP
Regulation of Glycolysis occurs at "irreversible" reactions
Enzyme/Reaction
Hexokinase (1)
(1)
(3)
glucose
glucose-6-Pi
Phosphofructokinase-1
fructose-6-Pi
bisPi
fructose-1,6-
Pyruvate kinase
(10) phosphoenol pyruvate
pyruvate
activator
inhibitor
glucose-6-phosphate
ATP
fructose-2,6-bisphosphate Citrate
AMP
ATP
fructose-1,6-bisphosphate Acetyl-CoA
AMP
ATP
Gluconeogenesis
Running glycolysis Backwards is a problem.
Three steps are irreversible.
In gluconeogenesis these three steps are avoided.
Reversing Step 10
O
O
CO2 + H2O
+ ATP
H+
C
O
pyruvate
H3C
O
C
ATP
ADP
CH2
O
O
C
GDP
CO2
C
GTP
O
phosphoenolpyruvate
C
H2C
O
oxaloacetate
pyruvate kinase
10
C
pyruvate carboxylase
C
O
guanosine
OPi
phosphoenol pyruvate
carboxykinase
O
Reversing Step 3
PiOCH2
O
fructose-1,6-bisphosphate
CH2OPi
HO
OH
OH
ADP
phosphofructokinase
3
ATP
PiOCH2
O
CH2OH
HO
fructose-6-phosphate
OH
OH
Reversing Step 3
PiOCH2
O
fructose-1,6-bisphosphate
CH2OPi
HO
OH
H2O
OH
ADP
fructose-1,6-bisphosphatase
phosphofructokinase
3
ATP
PiOCH2
O
CH2OH
HO
fructose-6-phosphate
OH
fructose-1,6-bisphosphate
OH
HPi
fructose6-phosphate
Reversing Step 3
PiOCH2
O
fructose-1,6-bisphosphate
CH2OPi
HO
OH
fructose-1,6-bisphosphate
H2O
OH
ADP
fructose-1,6-bisphosphatase
phosphofructokinase
3
ATP
PiOCH2
O
HO
fructose-6-phosphate
HPi
CH2OH
OH
fructose6-phosphate
OH
O
PiOCH2
O
CH2O
HO
OH
OH
P
H2O
O
PiOCH2
O
O
CH2OH
HO
O
OH
OH
HO
P
O
O
O
PiOCH2
O
CH2O
HO
OH
OH
P
H2O
O
PiOCH2
O
O
CH2OH
HO
O
OH
HO
OH
Instead of Making ATP from Fructose-1,6-bisphosphate and ADP the
phosphoanhydride is hydrolyzed.
P
O
O
Reversing Step 1
PiOCH2
O
glucose-6-phosphate
HO
OH
OH
OH
ADP
hexokinase
HOCH2
O
ATP
glucose
HO
OH
OH
OH
Reversing Step 1
PiOCH2
O
glucose-6-phosphate
HO
glucose-6-phosphate
OH
OH
H2O
OH
ADP
glucose-6-phosphatase
hexokinase
HOCH2
HPi
O
ATP
glucose
HO
glucose
OH
OH
OH
Reversing Step 1
PiOCH2
O
glucose-6-phosphate
HO
glucose-6-phosphate
OH
OH
H2O
OH
ADP
glucose-6-phosphatase
hexokinase
HOCH2
HPi
O
ATP
glucose
HO
glucose
OH
OH
OH
O
O
H2O
P
O
HOCH2
OCH2
O
O
O
HO
OH
HO
OH
OH
HO
OH
OH
OH
P
O
O
O
O
H2O
P
O
HOCH2
OCH2
O
O
O
HO
OH
HO
OH
OH
HO
OH
OH
OH
Instead of Making ATP from glucose-6-phosphate and ADP the
phosphoanhydride is hydrolyzed.
P
O
O
Fructose Metabolism
HOCH2
CH2OH
O
HO
OH
ATP
OH
ADP
hexokinase
fructokinase
O
O
P
O
O
CH2
O
CH2OH
HOCH2
HO
O
H2C
HO
OH
OH
O
OH
O
P
O
O
OH
fructose-1-phosphate aldolase
Fructose Metabolism
HOCH2
CH2OH
O
HO
OH
ATP
OH
ADP
hexokinase
fructokinase
O
O
P
O
O
CH2
O
CH2OH
HOCH2
HO
O
O
H2C
O
P
HO
OH
O
OH
OH
O
OH
fructose-1-phosphate aldolase
O
O
CH
H
C
OH
CH2OH
H2C
O
P
C
O
O
CH2OH
O
Fructose Metabolism
HOCH2
CH2OH
O
HO
OH
OH
ATP
ADP
hexokinase
fructokinase
O
O
O
P
O
CH2
CH2OH
O
HOCH2
HO
O
O
H2C
O
P
HO
OH
O
OH
OH
O
OH
fructose-1-phosphate aldolase
O
O
ADP
CH
H
C
H2C
ATP
OH O
O
P
O
O
CH
H
O
glyceraldehyde
kinase
C
OH
CH2OH
H2C
O
P
C
O
O
CH2OH
O
Mannose Metabolism
O
HOCH2
OH
HO
O OH
OH
ATP
ADP
O
P
O
CH2
O
OH
hexokinase
HO
O OH
OH
Mannose Metabolism
O
HOCH2
OH
HO
O OH
OH
ATP
ADP
O
P
O
O
OH
hexokinase
HO
O
CH2
O OH
OH
O
P
O
CH2
CH2OH
HO
O
phosphomannose
isomerase
O
OH
OH
Mannose is phosphorylated and converted to fructose-6-phosphate much like
glucose is.
Galactose Metabolism
O
O
UTP
HOCH2
ATP
ADP
O
HO
O
O
galactokinase
OH
O
P
O
O
P
O
HO
OH
OH
O
HOCH2
O
HO
OH
OH
HOCH2
P
O
O
O
OH
O
O
O
OH
P
O
O
P
O
Uridine
O
UDP-galactose-4-epimerase
HOCH2
UDP-glucose
glucose-1-phosphate
O
O
O
OH
O
HO
galactose-1-phosphate
uridyltransferase
OH
P
O
UDP-glucose
O
P
O
O
Uridine