Phosphoglucomutase
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Image:Phosphoglucomutase-1JDY.jpg Phosphoglucomutase (Template:EC number) is an enzyme that creates a glucose isomer by changing the site of the phosphate ion.
- Function in glycogenolysis
After glycogen phosphorylase has broken off a single glucose molecule from the greater glycogen structure, the free glucose has a phosphate group on its 1-carbon. This glucose-1-phosphate isomer cannot be metabolized easily. The enzyme phosphoglucomutase phosphorylates the 6-carbon, while subsequently dephosphorylating the 1-carbon. The result is glucose-6-phosphate, which can now theoretically travel down the glycolysis or pentose phosphate pathway.
- Function in glycogenesis
Phosphoglucomutase also acts in the opposite fashion when a large concentration of glucose-6-phosphate is present. In this case, it is the 1-carbon that is phosphorylated and the 6-carbon that is dephosphorylated. The resulting glucose-1-phosphate is then changed into UDP-glucose in a number of intermediate steps. If activated by insulin, glycogen synthase will proceed to clip the glucose from the UD-glucose complex and on to the glycogen molecule.