A mutase is an enzyme of the isomerase class that catalyzes the shifting of a functional group from one position to another within the same molecule. Examples of this are bisphosphoglycerate mutase, which appears in red blood cells and phosphoglycerate mutase, which acts in glycolysis. In glycolysis, it changes 3-phosphoglycerate to 2-phosphoglycerate. In particular it moves phosphate groups within a single molecule, for instance: phosphoglycerate mutase.