Biochemistry - Chemical Reactions in Living Cells Volume 2 - D. Metzler 1980

Types of reactions catalyzed by enzymes
Substitution at the phosphorus atom
Mutases

There is a group of phosphotransferases that catalyze the Transfer of phosphate groups from one position of a substrate molecule to another. An example is phosphoglucomutase; the reaction catalyzed by this enzyme proceeds with The intermediate formation of a phosphoenzyme. The phosphate group in the phosphoenzyme is attached to a reactive Serine residue and can be transferred to either position 6 or position 1 of the glucose phosphate molecule (step a or the reverse of step b in equation (7-26) [87].

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As a result of the two stages (a and b) of reaction (7-26), a reversible isomerization of glucose-1-phosphate to glucose-6-phosphate takes place, with the intermediate formation of glucose-1,6-diphosphate. Because the phosphorylated form of the enzyme is relatively unstable and undergoes Hydrolysis to yield the free enzyme (E) and inorganic phosphate, there is a separate kinase-catalyzed reaction (stage c). This stage ensures the generation of glucose-1,6-diphosphate, which rephosphorylates any free enzyme produced during the hydrolysis of the phosphoenzyme.

In the case of phosphoglycerate mutase, The Mechanism of the enzymatic reaction is similar, but the phosphate residue in the phosphoenzyme molecule is attached to an imidazole group [87a].