Uridine diphosphate glucose

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UDP-glucose ( uridine diphosphate -glucose ) is the product of a phosphorus pentoxide - exchange reaction of glucose-1 -phosphate ( G1P ) and uridine triphosphate (UTP).

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The formation of UDP-glucose is catalyzed by the enzyme UDP-glucose phosphorylase. The phosphate group of G1P attacks the α - phosphate group of UTP molecule to nucleophilic, where pyrophosphate is released. This is then degraded by the pyrophosphatase (inorganic phosphatase) by hydrolysis to two phosphate molecules. By hydrolysis of the pyrophosphate is the overall reaction exergonic:

G1P UTP → UDP -Glc PPi ( DG ° '= 0 kJ / mol)

PPi H2O → 2 Pi ( DG ° '= -33.5 kJ / mol)

→ G1P UTP H2O → UDP -Glc 2 Pi ( DG ° '= -33.5 kJ / mol)

Importance in the metabolism

UDP -glucose is the building block of glycogen synthesis and thus plays an important role in glucose metabolism. The release of UDP is a glucose molecule is attached to a Glykogenstrang. This reaction is catalyzed by glycogen synthase ( DG ° '= -13.4 kJ / mol). For the overall reaction to extend the Glykogenstrangs a glucose molecule ( glycogen ( n groups) UTP G1P → Glycogen (n 1 residues) UDP 2 P ) is a total of one molecule of UTP needed. The resulting UDP is by reaction with ATP (catalyzed by the Nucleosiddiphosphatkinase ) re-converted to UTP.