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