Metabolism of Carbohydrates - Uronic acid pathway

1. Ashok Katta

2. Uronic acid pathway
▪ Alternative oxidative pathway for glucose.
▪ Also called Glucoronic acid pathway.
▪ It is concerned with the synthesis of….
– Glucoronic acid
– UDP-glucose
– Pentoses
– Ascorbic acid (vitamin C) (in lower animals)

3. Reactions of
Uronic acid pathway
UDP-Glucoronic acid
Glucose 6-phosphate
Glucose 1-phosphate
UDP-glucose
D-Glucoronate
L-Gulonate
phosphoglucomutase
UTP
Mg+
PPi
NADP+
Mg+
NADPH+H+
UDP-glucose
pyrophosphorylase
UDP-glucose
dehydrogenase
H2O
Mg+
glucuronidase
UDP
Mg+
NADP+
NADPH+H+

4. L-Gulonate
L-Xylulose
Xylitol
L-Gulonolactone
2-keto-L-Gulonolactone
L-Ascorbic acid
D-Xylulose
D-Xylulose 5-phosphate
Hexose monophosphate Shunt
3-keto-L-Gulonate
H2O
NAD+
NADH+H+
CO2
NADP+
NADPH+H+
NADH+H+
NAD+
O2
Xylitol
dehydrogenase
L-Gulonolactone
oxidase
Essential Pentosuria

5. Effect of drugs on uronic acid pathway
▪ Administration of drugs such as……
Barbitol, chlorobutanol, etc
▪ Significantly increases the uronic acid
pathway to achieve more synthesis of
glucoronate from glucose.
▪ This is because, for detoxification of these
drugs glucoronate is requires.

6. Essential Pentosuria
▪ This an rare genetic disorder.
▪ Related to the deficiency of xylitol dehydrogenase.
▪ L-xylulose can not converts to xylitol.
▪ Affected individuals excrete large amount of L-xylulose
in the urine.

7. Thank you