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Dr. Howaida Nounou
UronicUronic Acid PathwayAcid Pathway
Dr. Howaida NounouBiochemistry department Sciences college
�It is an alternative oxidative pathway for glucose that, like
the pentose phosphate pathway, does not lead to
generation of ATP
� It includes oxidation of glucose to
1. Glucuronic acid: which is used in detoxication and 1. Glucuronic acid: which is used in detoxication and
enters in the formation of mucopolysaccharide.
2. Ascorbic acid
� It occurs in liver cytoplasm, mainly
Importance of UDP-Glucuronic acid
� conjugation to less polar compounds as bilirubin,
steroids and some drugs making them more water
soluble (detoxicated)
synthesis of glycosaminoglycans
UDP Glucuronic acid (active form) is needed in:
� synthesis of glycosaminoglycans(mucopolysaccharide) as heparin, hyaluronic acid…
� In plants and some animals (not Human) glucuronic acid
serves as a precursor of L-ascorbic acid
� The uronic acid pathway also provides a mechanism by
which dietary D-xylulose enter the central pathway
� Glucose 6-phosphate is isomerized to glucose 1-phosphate, which then reacts
with uridine triphosphate (UTP) to form uridine diphosphate glucose (UDPGlc)
in a reaction catalyzed by UDPGlc pyrophosphorylase
� UDPGlc is oxidized at carbon 6 by NAD-dependent UDPGlc dehydrogenase in a
two-step reaction to yield UDP-glucuronate
Glucose-6-(P)Phospho- UDPGlc
Formation of UDP-glucuronic acid
Phospho-
glucomutase
Glucose
Hexokinase
UDPGlc
dehydrogenase
UDPGlcpyrophosphorylase