Download Glycolysis

Enzyme Nomanclature
H
H-C-H
methyl
OH
C
-C-C
alcohol
H
aldehyde
C-C
=
O
C
Carbon dioxide
C-C=O
OH
O=C=O
C-C=O
keto
carboxylic acid
Glycolysis
Glycolysis
-conversion of glucose to pyruvate,
ATP & NADH + H+
C
ATP
O
Glucose
ADP
C
P
O
Glucose-6-P
(C6H12O6)
- IRREVERSIBLE (kinase reaction)--Glucokinase in liver, Hexokinase in skeletal
muscle
- takes 1 ATP
- now locked in cell because phosphorylated compounds can’t cross cell membranes by
diffusion and are not recognized by GLUT transporters
- Keeps intracellular free glucose levels very low to maintain facilitated diffusion
gradient
Glycolysis (cont.)
Step 2:
C
P
O
P
C
O
C
G-6-P Isomerase
Glucose-6-P
Isomerization (rearrangement of bonds)
-(ie Aldose
Ketose)
-frees the #1-C to be phosphorylated
Fructose-6-P
Glycolysis (cont.)
Step 3:
P
C
O
C
Fructose-6-P
ATP
ADP
(Phosphofructokinase
(PFK)-1)
Irreversible (kinase reaction)
- takes 1 ATP (-2 so far)
- phosphorylates fructose at 1-C
P
C
O
C
Fructose-1,6Bisphosphate
P
Glycolysis (cont.)
Step 4:
H
HO
H
H
H
H
C
C
C
C
C
C
H
H C O P
C O
+
HO C H
H
O
C
O P
H C OH
O
H C O P
H (aldolase)
H
OH
H
OH
DHAP
G-3-P
O P
DHAP= dihydroxyacetone phosphate (3-C)
H
F-1,6 BP (6-C)
G-3-P= Glyceraldehyde 3 phosphate (3-C)
Glycolysis (cont.)
Step 5:
C
C
C
O P
O
OH
H
Triose - P
Isomerase
DHAP
H
C
C
O P
OH
C
O
G-3-P
Isomerization - rearrangement of Bonds
- Ketose
Aldehyde
- 1 G-6-P
2 G-3-P
Glycolysis (cont.)
Step 6:
No Energy has been gained YET! -2 ATP
H
O
NAD+
NADH + H+
C
C
C
OH
O P
G-3-P
P
C
C
Pi
OH
O P
1, 3, D.P.G
-Phosphoglyceraldehyde dehydrogenase
-NAD+ reduced
-Aldehyde C oxidized to carboxylic acid
Glycolysis (cont.)
Step 7:
O
O
(2x)
C
C
P
OH
O P
ADP
ATP
(Phosphoglycerate
kinase)
1, 3, DPG
C
C
OH
O P
3 Phosphoglycerate
*1, 3 DPG has a G of -11.8 (ATP = -7.3)
Substrate level phosphorylation
O-
O
Glycolysis (cont.)
Step 8:
O-
O
C
OH
C O P
3 Phosphoglycerate
O
(Phosphoglycerate
mutase)
*mutase - transfers a phosphate group
O-
C O P
C OH
2 Phosphoglycerate
Glycolysis (cont.)
Step 9:
O
O-
O
O-
+H20
C
O
P
(Enolase)
C OH
2 Phosphoglycerate
This is a dehydration step. WHY?
G of PEP = - 14.8
C
O
P
C
Phosphoenol pyruvate
(PEP)
Glycolysis (cont.)
Step 10:
O-
O
+H20
C
C
O
O-
O
ADP
ATP
P
C
(Pyruvate kinase)
PEP
Generate 2 ATP via substrate
level phosphorylation
O
CH3
Pyruvate
Glycolysis (cont.)
step 6
Step 11:
O-
O
NADH + H
C
NAD
O
CH3
O-
O
H
(Lactate
Dehydrogenase)
Pyruvate
NADH + H oxidized to NAD
pyruvate reduced to lactate
C
OH
CH3
Lactate
LDH Isozymes
LDH-H has a high Km for pyruvate (lactate to pyruvate)
LDH-M has a low Km for pyruvate (pyruvate to lactate)
Glycolysis - Summary
Step 1:
- 1 ATP
Step 3:
- 1 ATP
Step 6:
+ 2 NADH + H +
Step 7:
+ 2 ATP phoshoglyceraldehyde kinase
Step 10:
+ 2 ATP pyruvate kinase
NET
+ 2 ATP via substrate-level phosphorylation
Key regulated enzymes: PFK and HK
Glycolysis - Summary (cont.)
Key enzyme: PFK (step 3)
-allosterically regulated
Activated by:
- AMP, ADP, PI
Inactivated by:
- ATP
- Citrate
- H+
CP and ATP Use During Exercise
Myokinase reaction 2 ADP
ATP + AMP
Glycolytic Flux with Graded Exercise
Over rest:
7.5x
39.5x
65x
323x
Over 35% VO2 max
----
5.2x
8.6x
43x
Cell to Cell Lactate Shuttle
Immunolabeling of LDH using
antibodies conjugated with 15nm
gold particles
Monocarboxylic
transporter
MCT 1-8
mMCT
pmMCT
Localization of
Krebs Cycle:
Glycolysis occurs in the
cytosol of cells.
Pyruvate transported
into the
mitochondrion to be
metabolized further.
Mitochondrial
Compartments:
matrix
cristae
intermembrane
space
inner
membrane mitochondrion
outer
membrane
 The matrix contains Pyruvate Dehydrogenase,
enzymes of Krebs Cycle, and other pathways, e.g.,
fatty acid oxidation & amino acid metabolism.
matrix
cristae
Mitochondrial
compartments
intermembrane
space
inner
membrane mitochondrion
outer
membrane
 Inner membrane infoldings, called cristae, contain
constituents of the respiratory chain & ATP Synthase.
The inner membrane is the major permeability barrier.
It contains various transport catalysts, including a carrier
protein that allows pyruvate to enter the matrix.
Pyruvate Dehydrogenase
H3C
O
O
C
C
pyruvate
HSCoA
O
O
H3C
NAD+ NADH
C
S
CoA
+ CO2
acetyl-CoA
Pyruvate Dehydrogenase, catalyzes oxidative
decarboxylation of pyruvate, to form acetyl-CoA.
Pyruvate
Dehydrogenase is a
large complex, with
multiple copies of
each of 3 enzymes:
E1, E2 & E3.
View an animation of the Pyruvate Dehydrogenase
reaction sequence.
O
H3C
C
S
CoA
acetyl-coenzyme A
Acetyl CoA, a product of the Pyruvate
Dehydrogenase reaction, is a central compound
in metabolism.
Activation of PDH with Graded
Exercise
Regulation of PDH during exercise
*
% of CHO from:
Glycogen
74%
91%
93%
99%
Blood glucose
26%
9%
7%
1%
% of pyruvate into:
CAC
100%
34%
26%
7%
HLA
0%
66%
74%
93%