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chapter 15
Carbohydrate Metabolism II: Gluconeogenesis, Glycogen Synthesis and Breakdown, and Alternative Pathways
G lu co se
6
-phosp hate
En doplasm ic
G lu co se-
6
-phosp hatase
G luco se
Inactive hep ato phosp horylase
CAMP
B ranched glycogen
dep endent
( 1,4 and 1.6 glucosyl units)
protein
Active
inactive
kinase
phosphorylase
phosphorylase
km ase
- '
:
.
D kgosacchandes
Active hep ato phosp horylase
Lysosom al
— J
. U n branched glycogen
-
1
,4-glucosidase
(
1,4
glucosyl units)
Limit dextnn
G lucose
^UDP
G lycogen synthase
D ebranching en zy m e
(amylO'i .6-giucosidase)
U D P -g iu co se
G luco se from the action
U D P -pyroph ospho rylase
of the debranchm g en zym e
U T P
G lucose
1
-phosphate
Lactate
rh o sp ro fru cto
Phosphoglucom utase
km ase
-1
Fructose 1.
6
-
Fructose
6
-pnosphate
G lucose
6
-phosphate
b.sphcsphate
G lu co se-
6
-phosp hate
transiocase
P h o s h a te
tra n s p o rte r
reticulum
G lucose transporter. G LU T -7
Location*» of the glycogen storage disease en/yme delects in the merall scheme of glycogenesis and
glycogenolvsis. The numbers corrcNpond to the disease t>pes listed in Table 15 -1
C IR C U L A T IO N
L IV E R
E X T R A H E P A T IC T IS S U E S
G lu c o s e
G lu c o s e
G lyco g en
G lu co se
G lu c o s e 1 -p h o s p h a te
U D P -g lu c o s e
G lu c o s e
6
-p h o s p h a te
G lu c o s e
6
-p h o s p h a te —
G lu c o s e 1-p h o s p h a te
f
\
G lu c o -
n e o g e n ic
p recu rs o rs
L ac tate
L ac tate
Lactate
FIGURE 15-14
Lactic acidosis and substrate cycling in glucose-6-phosphatase deficiency.
*Urinary lactate output is increased 10- to 300-fold in patients with type I glycogen
storage disease.
