Glycolysis
Metabolism: Catabolism + Metabolism
Energy-rich nutrients Macromolecules
CHO, fat, protein
Proteins, polysaccharides,
nucleic acids
ADP + Pi
Catabolism
Anabolism
ATP
Energy-poor products Precursors
CO2, H2O, NH 3
amino acids, sugars,
nitrogenous bases
Catabolism

Energy-yielding reactions

For non-photosynthetic organisms, two
sources of fuel
– Diet
• Fats, CHO, proteins
– Stored compounds
• Fats, starch, glycogen
Catabolism: The Big Picture
Carbohydrates
Proteins
Fats
Hexoses
Amino acids
Fatty acids
-keto acids
Pyruvate
Acetate
CO2
Krebs
cycle
O2
NADH
ADP
ATP
Carbohydrate Digestion
Ingested
– Starch, glycogen, cellulose, sucrose, lactose
Saliva
– -amylase
• All (14) split to make D-glucose
Stomach
– pH low
Carbohydrate Digestion
Small intestine
– Pancreatic -amylase
Brush border (small intestine)
– Sucrase: Glc + Fru
– Lactase: Glc + Gal
Glycogen Breakdown

Occurs in liver and muscles
Pi + (Glucose)n
Glu-1-P + (Glucose)n-1
Glycogen Breakdown
CH2OH
O
CH2OH
O
O
Pi
CH 2OH
O
O
Glycogen
phosphorylase
Glucose-1phosphate
CH 2OH
O
O
O
P
O
O
Glycogen Breakdown
In liver and muscle:
= non-reducing end
Glycogen phosphorylase releases 1 glucose
at a time, as glu-1-P, from non-reducing end
Glycogen Breakdown: Debranching
Pi
Pi
Pi
Pi
(1
Glycogen
phosphorylase
6)
Glycogen Breakdown: Debranching
Debranching
enzyme
Glycogen Breakdown: Debranching
Debranching
enzyme
+
Phosphoglucomutase
Glucose-1-P
Glucose-1,6bisP
P-enz + Glu-1-P
enz + Glu-1,6-bisP
Glucose-6-P
enz + Glu-1,6-bisP
Glu-6-P + P-enz
Importance of Glycolysis
Central energy-yielding path
Provides precursors for many biosynthetic
paths
Overlaps with pyruvate  glucose pathway
Illustrates enzyme mechanisms
Illustrates regulatory mechanisms
st
1
Stage of Glycolysis
Glucose
Glucose-1-P
Glucose-6-P
Fructose-6-P
Fructose-1,6-bisP
Dihydroxyacetone-P
Glyceraldehyde-3-P
Hexokinase Reaction
O
CH2OH ATP
O
HO
OH
ADP
CH2O
O
P
O
OH
Hexokinase
OH
HO
OH
2+
Mg
OH
OH
∆Gº= –16.7 kJ/mol
O
Hexokinase Reaction

Recall the “induced fit”
ATP
Glucose
Phosphohexose Isomerase
Glucose-6-P
68%

Fructose-6-P
32%
Keto-enol isomerization
H
O
H
C
C
H
C
OH
HO
C
H
G-6-P
OH
HO
CH2OH
C
OH
C
H
ene-diol
HO
C
O
C
H
F-6-P
Phosphofructokinase (PFK-1)
2+
Fru-6-P + ATP
Mg
Fru-1,6-bisP + ADP
∆Gº= –14.2 kJ/mol
Phosphofructokinase
Complex enzyme
– MW 360,000
 Rate-limiting step in glycolysis
 Major control point: allosteric regulation
– High ATP inhibits
– High AMP, ADP stimulates
– Other “fuels” alter activity
– Fru-2,6-bisP hormonal signal

Aldolase

Hexose  2 Trioses
Dihydroxyacetone-P
CH2OP
CH2OP
C
O
C
H
C
O
HO
C
H
H
C
OH
H
C
OH
H
C
OH
CH2OP
H
C
OH
Fructose-1,6bisphosphate
HO
Aldolase
H
H
CH2OP
Glyceraldehyde3-phosphate
∆Gº= +23.8 kJ/mol
Triose Phosphate Isomerase (TPI)
H
CH2OH
C
O
O
C
TPI
H
CH2OP
Dihydroxyacetone
phosphate
C
OH
CH2OP
Glyceraldehyde3-phosphate
∆Gº= +7.5 kJ/mol
Oxidation of Glyceraldehyde-3-P
Otto Warburg
1937-38
O
H
O
P
+
Pi NAD
NADH
O
C
OH
CH2OP
Glyceraldehyde3-phosphate
dehydrogenase
O
C
C
H
O
H
C
OH
CH2OP
∆Gº= +6.3 kJ/mol
O
Mechanism of Glyceraldehyde-P DH
CH2OP
H
C
OH
CH2OP
C
H
O
H
C
OH
H
C
OH
NAD +
NAD
+
SH
Cys
Cys
S
Mechanism of Glyceraldehyde-P DH
CH2OP
H
C
OH
H
C
OH
NAD +
Cys
S
CH2OP
+
H
H
NAD H
Cys
C
OH
C
O
S
Mechanism of Glyceraldehyde-P DH
CH2OP
CH2OP
H
NAD H
Cys
C
OH NAD +
C
O
S
H
NADH
NAD +
Cys
C
OH
C
O
S
Mechanism of Glyceraldehyde-P DH
CH2OP
H
O
O
P
CH2OP
O
H
O
NAD +
Cys
C
OH
C
O
S
C
OH
C
O
O
O
P
O
O
NAD +
Cys
SH
Phosphoglycerate Kinase
O
O
O
P
O
O
O
O
C
H
C
P
O
O
O
P
O
O
Ribose
Adenine
ADP
OH
CH2OP
O
O
O
C
H
C
OH
CH2OP
3-Phosphoglycerate
(3-PGA)
O
P
O
O
O
P
O
O
O
P
O
Ribose
Adenine
O
ATP
∆Gº= –18.5 kJ/mol
Phosphoglycerate Mutase
O
O
Mg2+
C
H
C
OH O
H
C
O
H
P
O
O
O
O
C
O
H
C
O
P
H
C
OH O
O
H
A covalent enzyme-phosphate intermediate (Phistidine) is involved, like phosphoglucomutase
∆Gº= +4.4 kJ/mol
Formation of Phosphoenolpyruvate
O
O
C
H
HO
C
C
H
H2O
O
O
H
P
O
O
O
C
O
C
enolase
O
O
C
H
∆Gº= +7.5 kJ/mol
P
O
H
O
ATP from PEP: Pyruvate Kinase
O
O
O
C
C
O
O
P
C
H
O
O
P
O
O
P
O
O
O
Ribose
Adenine
ADP
O
H
ATP
O
O
C
C
O
C
OH
C
H
O
H
enol pyruvate
C
O
CH3
pyruvate
∆Gº=
–31.4 kJ/mol
Summary of Glycolysis
+
Glucose + 2 NAD + 2 ADP + 2 Pi
2 Pyruvate + 2 NADH + 2 ATP + 2 H2O
(all in cytosol)
Side Products of Glycolysis Studies

Discovery of cofactors
– ATP
– NAD+

Methods of protein purification

Philosophical change
Side Products of Glycolysis Studies

Understanding of regulation

Demonstration of unity of biochemistry
Glycolysis in Motion: Preparatory Phase
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Jon Maber
Dept of Biochemistry and Molecular Biology
The University of Leeds, UK
http://bmbwww.leeds.ac.uk/designs/glysteps/home.htm
Glycolysis in Motion: Payoff Phase
Jon Maber
Dept of Biochemistry and Molecular Biology
The University of Leeds, UK
http://bmbwww.leeds.ac.uk/designs/glysteps/home.htm