Glucose-6-phosphate phosphoglucomutase reaction

To initiate glycogen synthesis, the glucose 6-phosphate is converted to glucose 1-phosphate in the phosphoglucomutase reaction ... 

The glucose-1-phosphate formed in reaction 2 is then converted to glucose-6-phosphate by phosphoglucomutase (reaction 4), an enzyme involved also in glycogen biosynthesis. Nucleoside diphosphate sugars such as UDP-glucose are widely used intermediates in polysaccharide biosynthesis. 

This is an enzyme of glycogen synthesis which can be estimated by u.v. spectroscopy using phosphoglucomutase in an auxiliary reaction and glucose -phosphate dehydrogenase in an indicator reaction [644]. 

The phosphoglucomutase reaction involves continual utilization and resynthesis of the cofactor, but it cannot cause the net synthesis of glucose-1,6-diphosphate. Two mechanisms have been found to increase the amount of this cofactor in each case glucose-l-phosphate is the phosphate acceptor but the phosphate donors are different for the two enzymes involved. Glucose-l-phosphate kinase requires ATP to carry out the reaction ... 

Leloir110(a) has described a conversion of D-mannosyl phosphate to D-mannose 6-phosphate by phosphoglucomutase, and here, too, the reaction requires catalytic quantities of a-D-glucose 1,6-diphosphate. The role of the latter is probably to generate a-D-mannose 1,6-diphosphate as follows. 

Glucose 1-phosphate produced by glycogen phosphorylase is converted to glucose 6-phosphate by phosphoglucomutase, which catalyzes the reversible reaction... 

The enzyme phosphoglucomutase catalyzes the interconversion of glucose-1-phosphate and glucose-6-phosphate (fig. 12.17). The interconversion occurs in two discrete steps by way of a phosphorylated enzyme and glucose-1,6-bisphos-phate. The reactions are... 

Experimental Determination of K eq and AG ° If a 0.1 M solution of glucose 1-phosphate at 25 °C is incubated with a catalytic amount of phosphoglucomutase, the glucose 1-phosphate is transformed to glucose 6-phosphate. At equilibrium, the concentrations of the reaction components are... 

Dispense 2.7-ml of this reaction cocktail in 10 small glass test tubes (13 X 100 mm), labeled A through J. To each of the 10 test tubes, add 100 (A of the 10-units/ml glucose-6-phosphate dehydrogenase solution and 100 /A of the 10-units/ml phosphoglucomutase solution. The total volume in each test tube after this step will be 2.9 ml. Refer to Table 15-2 to aid you in setting up the rest of the assay tubes. 

The second step in glycogenesis is conversion of glucose-6-phosphate to glucose-1-phosphate by phosphoglucomutase in a reaction similar to that catalyzed by phospho-glyceromutase. The phosphoryl group of the enzyme participates in this reversible reaction in which glucose-1,6-bisphosphate serves as an intermediate ... 

---