Glucose-1-phosphate uridylyltransferase

In the third step, glucose-1-phosphate is converted to uridine diphosphate (UDP) glucose, the immediate precursor of glycogen synthesis, by reaction with uridine triphosphate (UTP). This reaction is catalyzed by glucose-1-phosphate uridylyltransferase (or UDP-glucose pyrophos-phorylase) ... 

The building blocks of cellulose are D-glucose molecules in the py-ranose (six-membered ring) form, attached to uridine diphosphate (Figure 5.13). It is synthesized from alpha-D glucose phosphate catalyzed by the glucose-1-phosphate uridylyltransferase enz5mie ... 

This enzyme [EC 2.7.7.10], also known as UTP hexose-1-phosphate uridylyltransferase, catalyzes the reaction of UTP with a-D-galactose 1-phosphate to produce UDP-galactose and pyrophosphate (or, diphosphate), a-o-Glucose 1-phosphate can also function as a substrate, albeit not as effectively. 

T14. Severity of Clinical Symptoms Due to Enzyme Deficiency The clinical symptoms of two forms of galactosemia—deficiency of galactokinase or of UDP-glucose galactose 1-phosphate uridylyltransferase— show radically different severity. Although both types produce gastric discomfort after milk ingestion, deficiency of the transferase also leads to liver, kidney, spleen, and brain dysfunction and eventual death. What products accumulate in the blood and tissues with each type of enzyme deficiency Estimate the relative toxicities of these products from the above information. 

Answer In galactokinase deficiency, galactose accumulates in UDP-glucose galactose 1-phosphate uridylyltransferase deficiency, galactose 1-phosphate accumulates (see Fig. 14-12). The latter metabolite is clearly more toxic. 

Case B (c) Galactose 1-phosphate uridylyltransferase is an enzyme involved in conversion of galactose to glucose, which then can enter glycolysis. Absence of this enzyme leads to accumulation of galactose in the blood and excretion in the urine. A patient with this deficiency should be on a low-lactose diet (treatment 3). 

UDP-glucose Oc-D"galaciose 1 -phosphate uridylyltiaosferase Hexoiie-1 -phosphate uridylyltransferase... 

BL1643 was annotated to be a galactose 1-phosphate uridylyltransferase (EC 2.7.7.10) (GalT2), meaning the enzyme transfers the UMP (uridine monophosphate) unit of UTP (uridine triphosphate) to GallP. Although the LnpC protein did not have this activity, it showed UDP-glucose-hexose 1-phosphate uridylyltransferase... 

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