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CASE FILES: BIOCHEMISTRY
f_
1
P
2
= 0
3
-
/ v
-
/ V
ATP
AOP
HP)
ATP
ADP
HP)
glucose
glucose-6-P
G-6-P
fructose-6-P
F-6-P
0 dihydroxyacetone-P
lructose-1,6-bisP
FI ,6-BP
_ glyceraldehyde-3-P
GAP
7 ®
NAD+--------p
ct°O H
Y 0 ’
c h
3
*
pyruvate
10
Z Y
,o
C-OH
c^p)
II
CH
2
,o
Ç-OH
o
Ç-OH
V
H
20
- L
,
NADH
7
■ 7 Y
- r
.
o
f ®
P-enolpyruvate
PEP
2-P-glycerate
2PG
3-P-glycerate
3-PG
1,3-bisP-glycerate
1,3 BPG
1 Hexokinase
2 Glucose-6-P isomerase
3 6-Phosphofructokinase
4 Fructose 1,6-bisphosphate aldolase
5 Triosephosphate isomerase
6 3-Phosphoglyceraldehyde dehydrogenase
7 Phosphoglycerate kinase
8 Phosphoglyceromutase
9 Enolase
10 Pyruvate kinase
Figure 27-1. Glycolytic pathway.
*From glyceraldehyde 3-phosphate onward, two 3-carbon molecules/glucose proceed
through the pathway requiring a total of 2NAD+ and 4ADP producing a total of 4ATP,
2NADH, and 2H2O.
initiate the pathway one at the hexokinase step to phosphorylate glucose to
glucose 6-phosphate and a second to phosphorylate fructose 6-phosphate to
fructose 1,6-bisphosphate. Cleavage of fructose 1,6-bisphosphate by aldolase
yields two triose phosphates, glyceraldehyde 3-phosphate, and dihydroxyace-
tone phosphate, which is isomerized to glyceraldehyde 3-phosphate by triose
phosphate isomerase. The oxidation of the aldehyde group to the acid level
through the reduction of NAD+ to NADH with the concomitant binding of
inorganic phosphate to produce 1,3-bisphosphoglycerate is catalyzed by
3-phosphoglyceraldehyde dehydrogenase. This step requires NAD+ regeneration
to continue. Inorganic phosphate is present in tissues at such a high concen-
tration (typically 25 mM) as not to be limiting. The first substrate level phos-
phorylation occurs next wherein phosphoglycerate kinase catalyzes the transfer
of the acyl phosphate group of 1,3-bisphosphoglycerate to adenosine diphos-
phate (ADP), yielding ATP and 3-phosphoglycerate. Phosphoglucomutase
shifts the phosphate of 3-phosphoglycerate to carbon position 2 producing
2-phosphoglycerate. Enolase catalyzes the removal of the elements of water
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