Uridine 5-phosphate pyrophosphorylase

A specific uridine 5 -phosphate pyrophosphorylase has been purified from bacterial extracts (48, 60). The enzyme was found in a strain of lactic acid bacteria which could utilize uracil for growth, but was not found in one which required orotic acid. The latter strain contained only orotidine 5 -phosphate pyrophosphorylase. Some strains contain both enzymes (60). 

Sugar nucleotides are formed from sugar-l-phosphates and nucleoside triphosphates by specific pyrophosphorylase enzymes (Figure 23.18). For example, UDP-glucose pyrophosphorylase catalyzes the formation of UDP-glucose from glucose-l-phosphate and uridine 5 -triphosphate ... 

In fluorine-18 chemistry some enzymatic transformations of compounds already labelled with fluorine-18 have been reported the synthesis of 6-[ F] fluoro-L-DOPA from 4-[ F]catechol by jS-tyrosinase [241], the separation of racemic mixtures of p F]fluoroaromatic amino acids by L-amino acylase [242] and the preparation of the coenzyme uridine diphospho-2-deoxy-2-p F]fluoro-a-o-glucose from [ F]FDG-1-phosphate by UDP-glucose pyrophosphorylase [243]. In living nature compounds exhibiting a carbon-fluorine bond are very rare. 

The pyrophosphorylase of uridine 5 -(a-D-glucopyranosyl pyrophosphate), first detected in yeast,205 is widely distributed in Nature, and purified preparations of the enzyme have been obtained. With such a preparation from mammary gland, the phosphate 8 gave uridine 5 -(a-D-glucopyranosyl pyrophosphate) in about 95% yield.206... 

The glucose 1-phosphate is then activated to enable its incorporation into glycogen. This activation involves the expenditure of energy derived from the hydrolysis of a molecule of uridine triphosphate (UTP) by UDP-glucose pyrophosphorylase. 

UDP-glucose is synthesized from glucose 1-phosphate and uridine triphosphate (UTP) in a reaction catalyzed by UDP-glucose pyrophosphorylase. The pyrophosphate liberated in this reaction comes from the outer two phosphoryl residues of UTP. 

Glucose-l-phosphate and luidine triphosphate in the presence of UDPG pyrophosphorylase form uridine diphosphate glucose (UDPG) and pyrophosphate (see Fig. 2). Glucuronic acid is derived from UDPG... 

Fig. 20.5 The Leloir pathway of galactose metabolism and the uridine diphosphate (UDP) glucose pyrophosphorylase pathway. Gaik, galactokinase gait, galactose 1-phosphate uridyltrans-ferase gale, UDP-galactose 4-epimerase hex, hexokinase pgm, phosphoglucomutase Ugp, UDP-glucose pyrophosphorylase...

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